Colormetric sensor compositions and methods

ABSTRACT

The present invention provides novel compounds exemplified by pyrrolic nitrogens used as anion and neutral species recognition elements with an aromatic core as a signal group. Described are methods for the synthesis of various pyrrole aryl compounds as well as various applications for these compounds. Methods of use include the binding and detection of specific analytes in a mixture and, in some examples, the separation of the analyte from the mixture. Additional methods of use include the transport of therapeutic agents and the sensing of components, degradants, and impurities in foodstuffs.

[0001] This application claims priority to U.S. Provisional ApplicationNo. 60/136,467 filed May 28, 1999.

[0002] The government owns rights in the present invention pursuant toNational Institutes of Health (grant no. GM 58907 to Jonathon L.Sessler), the National Science Foundation (CHE-9725399 to Jonathan L.Sessler), the Texas ARP (grant 003658-102 to JLS) and a NIH PostdoctoralFellowship to Christopher B. Black.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The invention relates generally to compositions and methods forbinding and optically sensing anions, cations, and neutral species.Analytical methods for such species is the primary goal of opticalsensing. These methods may be qualitative or quantitative. Inparticular, compositions containing pyrroles as the key recognitionelement and a quinoxaline backbone as part of the compound, are shown toprovide a system with a built-in optical probe for selective sensing.

[0005] 2. Description of Related Art.

[0006] In the recent decades, supramolecular chemists have devotedconsiderable effort to developing systems capable of recognizing,sensing, and transporting anions (Dietrich, et al., 1997). This is anarea of effort that is considered both timely and important. Indeed,some 70 to 75% of all natural biological processes are thought toinvolve a negatively charged species (Schmidtchen, 1988).

[0007] Anion recognition constitutes an important problem area withinthe generalized field of supramolecular chemistry. Not surprisingly,therefore, it has been pursued extensively, particularly within thecalixarene domain. Indeed, most attention has focused on calixarenesystems that have been modified, via attachment to, or reaction with,electron deficient metal centers, so as to make more electrophilic thenormally π-electron rich calixarene moiety.

[0008] Anions constitute key components in food stuffs (e.g., fluoride,citrate and benzoate) and are products for, and pollutants from, modemagriculture (e.g., phosphate and nitrate) and can also act as potenttoxins (e.g. cyanide). One anion, pertechnetate, is critical toradio-diagnostic and therapy procedures and, in a different isotopicform, is a major radioactive pollutant. Given these few examples, it isclearly important that we have a means to readily monitor the presenceof these species in our everyday environment.

[0009] Among the range of biologically important anions, fluoride is ofparticular interest due to its established role in preventing dentalcaries (Kirk, 1991) Fluoride anion is also being explored extensively asa treatment for osteoporosis, (Riggs, 1984 and Kleerekoper, 1998) and,on a less salubrious level, can lead to fluorosis, (Wiseman, 1970 andGale, et al., 1996) a type of fluoride toxicity that generally manifestsitself clinically in terms of increasing bone density. This diversity offunction, both beneficial and otherwise, makes the problem of fluorideanion detection one of considerable current interest. Thus, whiletraditional methods of fluoride anion analysis, involving, e.g., ionselective electrodes and ¹⁹F-NMR spectroscopy remain important, there isan increasing incentive to find alternative means of analysis, includingthose based on the use of specific chemosensors. Particularly usefulwould be systems that can recognize fluoride anion in solution andsignal its presence via an easy-to-detect optical signature.

[0010] In the past few years, a wide range of anion sensors have beenproposed (sapphyrins, Sessler, et al. 1997; calixpyrroles, Gale, et al.1996 and Sessler, et al., 1998; cyclic polyamines, Dietrich, et al.,1981; Hoseini and Lehn, 1988) guanidinium (Dietrich, et al., 1981 andMetzger, et al., 1997)) that present varying degrees of affinity (andselectivity) toward anions such as F⁻, Cl⁻, H₂PO₄ ⁻ and/or carboxylates.Unfortunately, and in spite of considerable effort, a need for goodanion sensors remains. The number of anion sensors which can select forone biological anion over a range of anions present in vivo (phosphate,chloride, fluoride, etc.) remains at best, very limited. While thereexists small molecule sensors which can bind anions relatively well,they do so with little or no specificity. This is particularly true inthe case of fluoride anion where few, if any, easy-to-use signalingagents exist.

[0011] In addition to anion sensing, it is also desirable to developsensing elements capable of sensing cations and neutral species. Thepresence or absence, as well as the level of, various neutral molecularspecies is a useful diagnostic tool that can signal chemcialdecomposition. One example is the sensing of cis-3-hexenal (or chemicalderivatives thereof), a metabolite of the bacterial E. Coli, Salmonela,and Lysteria. Such sensors would find applicability in the food industryas detectors of food contamination and spoilage. They could, forinstance, be incorporated into food packaging materials.

[0012] Therefore, a need exists to develop methods and compositions forthe selective detection of anions, cations, and neutral species ingeneral, and for fluoride in particular. A motivation for thepreparation of new sensors is to obtain sensor compounds designed torecognize selectively a particular analyte within a range of species andproduce an easily detected signal.

SUMMARY OF THE INVENTION

[0013] The present invention provides novel compounds containing bothpyrrole-derived anion and neutral species recognition subunits and anaromatic core as the optical or visual signaling group to providechemosensors that allow for the convenient, color-based sensing ofanions. Most commonly, the aromatic core will be a quinoxaline moiety,but may be any aryl system having two pyrroles covalently bound toneighboring (but not necessarily directly ajacent) carbons on an arylmoiety through a C—C single bond connecting pyrroles and the aromaticmoiety.

[0014] Formula I illustrates the general pyrrole-aryl systems (α,α andβ,β substitution on the pyrrole rings) along with the specificpyrrole-quinoxaline analog shown directly below. Note that the pyrrolesubstitution may also be mixed, i.e., α,β or β,α. As used herein, “aryl”means any aromatic system consisting of one or more rings which may behomonuclear or heteronuclear, and which may or may not contain aromaticor non-aromatic side groups (substitution), and which may be furthercomplexed to one or more metals. The present invention further providesmethods of use and synthetic schemes for these novel compounds.

[0015] The present invention provides novel compounds exemplified by thepyrrolic nitrogens used as anion recognition elements with an aromaticcore as a signal group. The compounds of the present invention aretermed pyrrole-aryls, and as used herein, the compounds of the presentinvention which, at least, combine these two elements will be referredto as such. Although not shown above, the pyrrole carbon atoms may alsobe substituted. The aryls may or may not contain heteroatoms.Subsituents may include, but are not limited to, hydrogen, alkyl,hydroxyalkyl, glycol, polyglycol, amino, nitro, halo, cyano, aryl,heteroaryl, thio, thioalkyl, amide, ester, acyl, or carboxy and may bethe same or different at each occurrence.

[0016] Compounds of the present invention may be prepared by acondensation between a 1,2-diamine and a 2,3-dipyrryl ethanedione asshown in Scheme 1.

[0017] While specific substituents are listed above, the quinoxalineanalogs may have a wider variability of substituent groups. R₁ and R₂may be, individually at each occurrence, hydrogen, alkyl, hydroxyalkyl,glycol, polyglycol, amino, nitro, halo, cyano, aryl, heteroaryl, thio,thioalkyl, amide, ester, acyl, or carboxy. Although not shown above, anyor all of these possible substitutions may be present on the remainingavailable carbon atoms of the quinoxaline. Additionally, any or all ofthese same possible substitution combinations may also be present on theα or β positions, or on both the α and β positions (relative tonitrogen) of the pyrrole rings.

[0018] Oxalyl chloride, o-phenylenediamine, 4-nitro-1,2-diaminobenzenewere purchased from Aldrich and used without further purification.4,5-Diamino-1,2-dimethoxybenzene was prepared according to the method ofSessler, 1992. 4,5-Dinitro-1,2-diaminobenzene was prepared according tothe method of Cheeseman, 1962.

[0019] Thus, in a second respect, the present invention is the2,3-dipyrryl-ethanediones used to produce the pyrrole-aryls. In thisaspect of the invention the dipyrryl-ethanediones are of Formula II:

[0020] wherein individually at each occurrence, each of R₁,- R₆ are thesame or different and are hydrogen, alkyl, hydroxyalkyl, glycol,polyglycol, amino, nitro, halo, cyano, aryl, heteroaryl, thio,thioalkyl, amide, ester, acyl, or carboxy. Though not shown thedi-β-linked diketone (bridging group attached to pyrroles in position βto nitrogen atoms) is within this family, as is the mixed α, β-linkeddiketone.

[0021] These dipyrryl-ethanediones may be produced by reaction of apyrrol either commercially available or obtainable through syntheticmethods known to one of skill in the art, with oxalyl chloride asrepresented in Scheme 1 to generate a variety of dipyrryl-ethanediones.

[0022] Further to this, the present invention provides a new set ofnovel dione compounds generated from the reaction of bipyrroles,terpyrroles etc. with oxalyl chloride to generate the compounds ofFormula III:

[0023] wherein individually at each occurrence, each of R₁-R₇ are thesame or different and are hydrogen, alkyl, hydroxyalkyl, glycol,polyglycol, amino, nitro, halo, cyano, aryl, heteroaryl, thio,thioalkyl, amide, ester, acyl, or carboxy and n=0-10. The analogousR_(x) groups on either side of the diketone bond may be the same ordifferent (i.e., R₁, R₂, . . . R_(x) on one side of the diketone bondmay be the same or different from the corresponding R₁, R₂, . . . R_(x)on the opposite side, etc.; additionally, the R₄ and R₅ groups may havevariability amongst individual pyrrole subunits; e.g. R₄ on any givensubunit may be the same or different from a corresponding R₄ on anyother subunit). Symmetry in substitution along the axis bisecting thediketone bond or among any pyrrole subunit is not required and maximumvariability in substitution is possible so long as the general formulais followed.

[0024] These novel diones may then be used to generate novelpyrrole-aryl compounds such as 2,3-di(bipyrryl)quinoxalines (n=0),2,3-di(terpyrrylquinoxalines (n=1), 2,3-di(tetrapyrrylquinoxaline (n=2)etc. The preferred route is via a condensation reaction involving thetwo ketones with an aryl compound.

[0025] It is further contemplated that the 2,3-dipyrryl-ethanediones mayundergo reaction with any 1,2-diamine under conditions outlined inScheme 1 to generate a variety of new compounds for anion sensing asrepresented by Formula IV (functionalized quinoxaline analogs) andFormula V (functionalized pyrrole, functionalized quinoxaline analogs),respectively.

[0026] In Formula IV and V, respectively, individually at eachoccurrence, each of R₁-R₄ and R₁-R₁₀ are the same or different and arehyrdogen, alkyl, hydroxyalkyl, glycol, polyglycol, amino, nitro, halo,cyano, aryl, heteroaryl, thio, thioalkyl, amide, ester, acyl or carboxy.Note that the quinoxaline analogs are used for illustrative purposes inthe above examples. It is readily apparent to one of ordinary skill inthe art that an appropriate aryl or substituted aryl may be used inplace of quinoxaline for the more generalized pyrrole-aryl arylcompounds. As earlier discussed, the only requirement is orbital overlapof the ring systems comprising the aryl and pyrrole groups which arealtered by bond rotation upon binding of substrate (anion, cation, orneutral atom or molecule):

[0027] The pyrrole groups are preferably on, but need not be on,adjacent carbons of the aryl moiety. Note that the nitrogen atoms may bedeprotonated to afford cation-binding systems.

[0028] 2,3-dipyrrol-2′yl-5,6-dicyanopyrazine (Example 30) is an exampleof an analogous pyrrole-aryl sensing compound that does not contain thequinoxaline moiety. The present invention provides a solution to theneeds described herein above by producing compounds and methods forselective sensing. In particular, the preferred pyrrole-aryl compoundsof the present invention have the ability to selectively bind fluorideanion over biologically important competitors such as chloride andphosphate and in doing so, produce a color change from yellow to orangein the case of 1 and from orange to purple for 3 and 8 which is, in somecircumstances, visible to the naked-eye. It was further found that forthese particular analogues, organic solvents encourage fluoride bindingwhile polar solvents, such as methanol or water, lead to fluoridedissociation. This property would allow for the original sensor to beregenerated by changing solvents once the sensing is complete.

[0029] The compounds of the present invention are particularlycontemplated for use in fluoride sensing, especially in the presence ofother biologically common anion species. While analogues such as 3 maydisplay other anion sensitivities, the ability to selectively sensefluoride anion would be particularly useful for many purposes as furtherdiscussed in Examples 40 and 42.

[0030] Therefore, an aspect of the present invention is the developmentof analytical methods for species which are selectively bound by thepyrrole-aryl compounds. As used herein, “analysis” means bothquantitative and qualitative analysis. As used herein, optical methodsincluded instrumental spectroscopic methods as well as visualobservation. While the focus is on optical and visual analyticalmethods, electrochemical methods employing the pyrrole-aryls as sensingelements are also envisioned. Time-based analytical methods, such asthose monitoring changes in fluorescence lifetimes (as well as otherphotophysical temporal phenomena) measurements are also envisioned.Either of these analytical examples would be sensitive to themodification of the molecular electronic structure of the sensingcompound which would be caused upon substrate binding. Many otheranalytical measurements sensitive to such changes in electronicstructure and which are known to those of skill in the art would beapplicable in the present invention.

[0031] It is contemplated that the pyrrole-aryls of the presentinvention have a wide variety of uses. A range of compounds with a largenumber of substituents fall within the scope of the present invention.The precursor molecules, the starting pyrrole or dione, may bederivatized as desired or the pyrrole-aryl may be modified postsynthetically to yield compounds with desired substituents. Therefore,it is contemplated that the selectivity of the pyrrole-aryl compounds ofthe present invention will have a number of different selectivitiesachieved by variation of substituents within the structure.

[0032] It is also envisioned that the binding and sensing capabilitiesof the pyrrole-aryls can be further exploited by surface immobilization.Functionalization of the pyrrole-aryl with reactive groups would affordthe ability to attach them to solid phases. Polymer phases, silica andpolystyrene, among others, are solid surfaces which find applicabilityin this embodiment of the invention. Surface immobilization is useful inthe separation sciences, in the fabrication of sensors such as fiberoptic probes, as well as other applications. In the field of separationscience, surface immobilization can be used to fabricate novelstationary phases. In fiber optic sensing application, immobilization ofthe sensing element on the distal end of a fiber optic tip can be usedto construct sensors useful for remote analyses. Fiber optic sensors areknown to be amenable to remote sensing, such as in vivo, in vitro orin-situ sensing. In vivo applications would involve miniaturization ofthe fiber optic tip, thus the high sensitivity achievable with thepyrrole-aryls is particularly advantageous. In the area of foodstuffanalysis, surface immobilization of the pyrrole-aryls onto fiber opticsensors, or alternatively, onto packaging components of foodstuffs isenvisioned to afford a quick, convenient way to monitor spoilage.

[0033] Additionally, the pyrrole-aryls of the present invention may bemodified to increase aqueous solubility for use analytically or astherapeutic agents. In sensing applications, modification of solubilitymay be used to optimize a sensing element for the particular environmentto be interrogated. This is performed through functionalization of thepyrrole-aryl compounds with groups that impart water solubility. Polargroups, especially those which readily carry a charge under variousconditions, are candidates for such functionalization. Carboxy, hydroxy,and amine groups are most obvious but others are possible. Enhancingwater solubility is useful therapeutically by enhancing bioavailability.

[0034] Additional modifications are envisioned in which thepyrrole-aryls may be incorporated into macrocyclic compound.Porphyrin-type complexes are but one example further described below. Byincorporating the binding site into a macrocyclic compound, novelcompounds may be made to optimize transport of therapeutic agents, or totailor the sensing element for a specific application. Metal-linkedsystems of pyrrole-aryls are another aspect of the present invention.These may be prepared by first preparing silyl derivatives having, forexample, TMS groups appended. Subsequent deprotection and reaction witha metal salt will afford metal linked systems.

[0035] Therapeutic uses of the compounds of the invention are alsodescribed. The binding capabilities may be exploited for uses astransporting agents. Anionic, cationic, and neutral species, throughbinding to the appropriate pyrrole-aryl, can be directed in vivo toareas where their therapeutic effect is optimally realized. The highaffinity for a number of these species for chloride ion has potentialapplicability in the treatment of cystic fibrosis. Cystic fibrosis ischaracterized by a reduced ability to effect chloride ion transport atthe cellular level. involves the localized introduction of chloride ion.A means for enhancing the transport of chloride ion is therefore usefulin such treatments. While this is one specific example, the ability totransport therapeutically active agents is expected to have widerapplicability. This has the beneficial advantages of allowing for moreefficient and lower dosages, which minimizes side and toxicity effects.

[0036] The compounds of the present invention provide a furtheradvantage in the ease with which the pyrrole-aryls can, in light of thepresent disclosure, be modified. The synthetic steps are relativelysimple and inexpensive to carry out. As the optical and bindingproperties can be controlled by the types of substituents present, thisallows enough flexibility to accommodate a number of applications aswell as the fine tuning of desired properties, for application in aspecific environment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The following drawings form part of the present specification andare included to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein.

[0038] FIG. 1 provides a view of the hydrogen bonded complex of [1•F]⁻as it extends along the a axis. Hydrogen bonding interactions areindicated by dashed lines. The relevant geometry for these interactionsare: N1-H1N . . . F1 (related by x-1, y, z), N F 2.629(2) Å, H . . . F1.63(3) Å, N—H . . . F 169(2)°; N17-H17 F1, N . . . F 2.640(2) Å, H F1.69(3) Å, N—H . . . F 168(2)°; O1w-H1w F1, O . . . F 2.590(2) Å, H F1.70(3) Å, N—H O 177(3)°.

[0039] FIG. 2 is a view of the 2,3-dipyrrylquinoxaline unit 1 in itsanion-free water complex.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0040] The present invention generally relates to methods andcompositions for anion and neutral species binding, analysis andrecognition. As used herein, “analysis” encompasses both quantitative orqualitative analysis. In particular, the compounds and methods of thepresent invention utilize pyrroles as the key recognition-inducingcomponent and aryl groups as optical reporting group. Many of thedisclosed compounds contain quinoxalines as the aryl as part of thebackbone structure to provide systems with built in chromophores and/orfluorophores for optical sensing. While quinoxaline is preferred, theinvention is not limited to sensing compounds with this aryl component.

[0041] With reference to the substituents contemplated for use inaccordance with the present invention, alkyl may be of the repeatingunit —(CH₂)_(n)CH₃. The number of repeating units within an alkylsubstituent may be up to fifty, preferably up to 20 and more preferablyfrom 0-10. Representative examples of alkanes include methane, ethane,straight chain branched or cyclic isomers of propane, butane pentanehexane, octane, nonane and decane. Representative examples ofsubstituted alkyls include alkyls substituted by two or more functionalgroups as described herein. Hydroxyalkyls includes alcohols of alkylgroups as defined previously. Representative examples of hydroxyalkylsinclude alcohols of methane, ethane, straight chain branched or cyclicisomers of propane, butane, pentane hexane, octane, nonane and decane.Hydroxyalkyl is meant to include glycols and polyglycols. Representativeexamples of glycols include diols of ethane, straight-chain, branched orcyclic isomers of propane, butane, pentane hexane, octane, nonane anddecane. Representative examples of polyglycols include polyethyleneglycol, polypropylene glycol, polypropylene diol and polybutylene diol.Representative examples of oxyalkyls include the alkyl groups definedherein above having ether linkages.

[0042] Representative examples of thioalkyls include thiols of an alkylas described herein above including thiols of ethane, thiols ofstraight-chain, branched or cyclic isomers of propane, butane, pentane,hexane, heptane, octane, nonane and decane. Sulfate substituted alkylsinclude alkyls as described above substituted by one or more sulfategroups, a representative example of which is diethyl sulfate((C₂H₅)₂SO₄); they also include simple anionic sulfate or sulfonatesubstituents such as —C₂H₅SO₃ ⁻.

[0043] As used herein, aryl refers to a compound whose molecules havingeither the pi-conjugated ring of benzene or the condensed rings of theother aromatic derivatives including heteroatom-containing aromaticderivatives (heteroaryls). They may additionally contain non-aromaticsubsituents as side groups or be linked to metals. Representativeexamples include benzene, naphthalene, phenanthrene, phenanthroline, andanthracene. A heteroaryl compound, as used herein, refers to a compoundwhich contains more than one kind of atom in an aromatic ring.Representative examples include pyridine, pyrimidine, furan, thiophene,pyrrole and imidazole.

[0044] Representative examples of amines include primary, secondary andtertiary amines of an alkyl as described herein above.

[0045] Representative examples of carboxy groups include carboxylicacids of the alkyls described above as well as aryl carboxylic acidssuch as benzoic acid. Carboxy groups also include derivatives ofcarboxylic acids such as esters, amides, acyl halides, anhydides, andnitriles. Representative examples of carboxyamides include primarycarboxyamides (RCONH₂), secondary (RCONHR′) and tertiary (RCONR′R″)carboxyamides where each of R′ and R″ is a functional group as describedherein and the carboxy group is as defined herein above.

[0046] Representative examples of ester groups include compounds of theform RCOR′ where the R group is an alkyl as described herein above andwhere R′ is a functional group as described herein. Representativeexamples of acyl groups include acyl derivatives RCO- or ArCO-, whereinR is an alkyl as described herein above and Ar is an aryl group asdefined herein.

[0047] The choice of metal ion for complexing to analogues of thepresent invention will generally be dependent on the use or intended useof the analogue. For example, representative metals for the porphyrinderivative include Zn, Cu, Pd, Ni, Fe, Co, Ru, Rh, and Os.

[0048] In one embodiment a method for anion sensing is disclosed usingcompounds of general Formula I shown herein above. Importantly, thegeneral structures may possess substituent (R) groups at any carboncapable of accommodating such substituents (i.e., those bound to atleast one hydrogen atom in the general structures) each R being definedas above.

[0049] The synthesis of compounds represented in Formula I is outlinedin Scheme 1. In this embodiment the substituents R₁ and R₂ areintroduced during the synthesis on the aryl 1,2-diamine as shown. Itwould be well appreciated by one of skill in the art, in light of thepresent disclosure, that a wide variety of aryl 1,2-diamines may becondensed with a 1,2-dipyrryl ethanedione to provide a vast array ofdifferent compounds and that any or all of the remaining positions onthe 1,2-diamine may bear substituents as exemplified by Formula IV.

[0050] Additionally, compounds derived from those represented by FormulaI are contemplated for the formation of metal complexes. For example,structure 9 may be condensed with 1,10-phenanthroline-5,6-dione to formcompound 13. An alternate condensation of structure 9 with5,6-diamino-1,10-phenanthroline affords structure 14. Both of theseexamples are shown in Example 34 where the metal binds through thephenanthroline nitrogens. Furthermore, compounds with alteredfluorescence, represented by 15 and 16, may be synthesized usingconditions similar to those provided in Example 34. Additionally, thosesyntheses detailed in other Examples could be effected using theappropriate dione.

[0051] Further variants may be produced by using a porphyrin dione inthe condensation to form a compound exemplified by structure 17 (Example34), bearing a range of substituents at the meso and β-pyrrolicpositions. The porphyrin may be metallated using standard techniques togenerate a range of compounds containing various metals (for example Zn,Cu, Pd, Ni, Fe, Co, Ru, Rh, Os). For the substituents shown in structure17, individually at each occurrence, each of R₁, R₄, R₇, R₁₀, is ahydrogen atom, alkyl, aryl or heteroaryl and individually at eachoccurrence, each of R₂, R₃, R₅, R₆, R₈, R₉ is a hydrogen atom, alkyl,aryl or heteroaryl, halo, cyano, acyl, carboxyl, carboxy ester,carboxyamide, nitro or amino. While these are the preferredsubstituents, a wider range of substitution is possible and may even bedesirable for given applications. One of skill in the art can appreciatethe wide range of substitution possible. These porphyrin containingcompounds are contemplated for analytical applications, particularly asredox-based and/or optical sensors.

[0052] Other possible metal-containing analogs include pyrrole-aryltethered metallocenes such as ferrocene. Additionally, crownether-derivatized pyrrole-aryls can be used as metal bearing agents.Other host-guest species such as cyclodextrins may be coupled covalentlyto the pyrrole-aryls. Metallocenes, crown-ethers, and cyclodextrins actas substrate binders and catalysts in their own distinctive chemistries.Binding to the pyrrole-aryls will produce novel, synergistic bindingeffects. These are expected to further extend the usefulness of thesenovel species to electrochemical applications, particularly foranalytical sensing. It is envisioned that the metal-complexedderivatives will be useful as ion channels. The selective binding andtransport capabilities of such “pore-forming” species will haveapplication as transport agents therapeutically and as sensorsanalytically.

[0053] The dipyrrole quinoxalines of the present invention may also bemodified post-synthetically to introduce a variety of substituents atthe α and/or β pyrrolic positions, R₃ and R₄, as shown in compound 18(Example 35). The substituents R₁ and R₂ are as previously described, R₃and R₄ may be the same or different, and may be halides, including, iodoand bromo, alkyl, aryl, heteroaryl, acyl, nitrile, carboxy amide,carboxy ester or sulfide. The introduction of these substituents allowsfor further modification of properties for a given compound. Usingprotocols well known in the art, the dibromo or diiodo compounds may beused to generate a further range of α substituted compounds such asthose provided by structure 19. Compounds such as 20, may be used insubsequent reaction with a metal salt, such as [PdCl₂(PEt₃)₂], {i.e.,bis(triethylphosphine) palladium(II) dichloride, or phosphino-platinumdichloride complexes, following removal of the TMS groups to affordmetal linked systems.

[0054] The pyrroles used in accordance with the present invention toprepare the pyrryl-quinoxalines, may be derivatized as represented inScheme 5, structure 21 (Example 36). The pyrrole units with R₁-R₃substituents may, in some cases, be commercially available or in otherinstances may be prepared through synthetic methods well known to one ofskill in the art.

[0055] The 1,2-dipyrryl-ethanediones used in the present invention maybe generated using the above-described pyrroles in a reaction withoxalyl chloride to provide many different 1,2 dipyrryl-ethanediones asshown in Scheme 5. Substituents R₁, R₂ and R₃ are alkyls, hydroxyalkyls,substituted alkyls, amines, halo, cyano, aryl, heteroaryl, thio,thioalkyl, amide, ester, acyl and carboxy. Representative examplesinclude those described previously with the preferred substituents aslisted in Example 36 for compound 22.

[0056] Additionally, several other compounds are contemplated for use inthe reaction with oxalyl chloride to generate a series of diones. Inparticular, many different polypyrroles, bipyrroles (n=0), terpyrroles(n=1), up to and including n=10 may be employed as shown in Scheme 6(Example 36) to generate compounds exemplified by structure 24. R₁through R₇ are alkyl, hydroxyalkyl, glycol, polyglycol, amino, nitro,aryl, heteroaryl, acyl, halo, carboxy ester, carboxy amide and carboxyas previously described, such that R₁-R₇ may be the same or different ateach occurrence and n is 0-10, with R₁ through R₇ as H and n=0 beingpreferred.

[0057] It is further contemplated that quinoxaline compounds of thepresent invention with a free α-position may undergo further reaction asshown in Schemes 7A-7D (Example 37) for incorporation into macrocyclesfor use as sensing/transporting agents, and optical display devices. Awide variety of conditions known to one of skill in the art, may beemployed to promote reaction of the remaining α-free position on thepyrrole rings as shown in Example 37. These compounds are as representedby structures 25-32, and thus fall within the scope of the presentinvention.

[0058] Further sources of synthetic variation may be generated usingdiones comprised of various heterocyclic rings as shown in Example 38.These compounds may provide alternate selectivity for a variety of otheranalytes, such as metal ions in the case of the furan, thiophene,pyridine and pyridine N-oxide derived systems.

[0059] Another source of variation involves the use of dianions ofeither the 1,2-di-pyrrylethanedione or the 2,3-di-pyrrylquinoxalines, asrepresented in Example 39, in accordance with the present invention.These dianions are contemplated for use as ligands for the generation ofmetal complexes. Such compounds would find use in the areas of molecularwires and display devices.

[0060] It is particularly contemplated that the pyrrole quinoxalinecompounds of the present invention will be of use as anion sensors.Example 40 provides a further discussion. It is further contemplatedthat the preferred compounds will find utility as novel fluoride anionsensors and receptors, and other examples will find use as chloride andphosphate sensors and receptors. The unsubstituted pyrrolic nitrogensprovide anion binding sites as detailed in Examples 31-33. Furthermore,the pyrrole quinoxaline compounds of the present invention provide aquinoxaline core as a chromophoric signal group for the color-basedsensing of anions.

[0061] Any one of a wide variety of anions may be detected using thepyrrole-aryls or alternate heterocyclic quinoxalines in accordanceherewith. These anions include, but are not limited to, cyanide anion,phenolate anion, carboxylate anion, sulfate anion, sulfonate anion,nitrate anion, nitrite anion, bromide anion, pertechnetate anion,perrhenate anion, chloride anion, phosphates and phosphonates.

[0062] Additionally, the disclosed methods are contemplated for bindingor complexing a range of analytes, including anion, cations and neutralspecies, but particularly anions and neutrals. Therefore, alsocontemplated are phosphate-containing compounds, including simple alkylor aryl phosphates, alkyl phosphonates, nucleotides, oligo- andpolynucleotides such as DNA, RNA and anti-sense constructs andnucleotide analogues. Representative examples of phosphates includephosphate or polyphosphate groups. Representative examples of phosphatesubstituted alkyls include alkyls as described above substituted by oneor more phosphate or polyphosphate groups. Representative examples ofphosphonate substituted alkyls include alkyls as described abovesubstituted by one or more phosphonate groups.

[0063] The term nucleotide, as used herein, refers generally to anymoiety that includes within its structure a purine, pyrimidine, ornucleic acid with a ribose group and at least one phosphate group, orany derivative of these such as a protected nucleotide. Thus the termnucleotide includes adenosine tri-, di- and monophosphate, guanosinetri-, di- and monophosphate, cytidine tri-, di- and monophosphate,thymidine tri-, di- and monophosphate, uridine tri-, di- andmonophosphate and xylo-guanosine monophosphate a well as any nucleotidederivative based upon these or related structures.

[0064] As discussed previously, the increased specificity and opticalanalysis makes this class of anion sensors considerably more effectiveat anion recognition and detection than other classes of molecules. Thecapacity of pyrrole-aryls and analogues thereof, to effect specificsensing of anions in general, and fluoride in particular, iscontemplated to be advantageous for use in vitro and in vivo. Forexample, the disclosed compounds may be used to effect the constructionof electrodes (analogous to pH sensing) or to fiber optic cables foranalysis of drinking water, in vitro, or for in vivo fluoride sensing inthe analysis of bone density. In addition to optical sensors, otherapplications are contemplated such as chromatography. Here for example,compounds 1-3 are coupled to a solid support. The pyrryl-quinoxalinescan be attached to solid supports, via condensation reaction betweencomplementary functional groups on the quinoxaline and the solidsupport, e.g., amine on quinoxaline with carboxyl on solid support toyield an amide linkage, or a carboxyl group on the quinoxaline with anamine or hydroxyl on the solid support to give an amide or ester linkagerespectively. These coupled compounds may be used to separate variousanions from each other and from other species in the mixture.

[0065] Additionally, the binding and/or sensing of fluorinated compoundsis also contemplated. It is well established that fluorinatedhydrocarbons are damaging to the atmosphere, as well as to humans, andthat fluorinated phosphates are extremely toxic when ingested, forinstance from chemical weapons. In order to increase solubility inaqueous solutions, derivatives containing additional pyrroles in thepyrrole-aryl system as outlined in Example 41. This would allow foranalysis of fluoride levels in blood samples as well as a treatment forany detected fluorosis.

[0066] In the detection of fluoride anion as described in Examples31-33, the preferred solvent is an aprotic one with dichloromethaneparticularly preferred. However, other solvents are contemplated for theappropriate analogues as described previously.

Immobilization on Solid Supports

[0067] The target pyrrole-aryl sensing compound can be covalentlyattached to a solid support using any of the number of methods commonlyemployed in the art to immobilize molecular species to solid supports.Covalent attachment of the sensing compound to the solid support mayoccur by reaction between a reactive site or a binding moiety on thesolid support and a reactive site or another binding moiety attached tothe sensing compound or via intervening linkers or spacer molecules,where the two binding moieties can react to form a covalent bond. Forexample, binding of a sensing compound to a solid support can be carriedout by reacting a free amino group of an amino-functionalized sensingcompound with a reactive carboxy of the solid support. Similarly thereaction of alcohol groups and the derivatized and native SiOH groups ofsilica can afford immobilization.

[0068] Coupling of a sensing compound to a solid support in this way maybe carried out through a variety of covalent attachment functionalgroups. Any suitable functional group may be used to attach the sensingcompound to the solid support, including but not limited to disulfide,carbamate, hydrazone, ester, N-functionalized thiourea, functionalizedmaleimide, mercuric-sulfide, gold-sulfide, amide, thiolester, azo, etherand amino. The solid support for use in separation science or sensortechnologies may be made from a wide variety of materials, such assilica, cellulose, nitrocellulose, nylon membranes, controlled-poreglass beads, acrylamide gels, polystyrene, activated dextran, agarose,polyethylene, functionalized plastics, glass, silicon, brominated Wangresin, Merrifield resin, agarobiose, carboxypolystyrene HL, and TG-aminoresin. Some solid support materials may require functionalization priorto attachment of the sensing compound. Solid supports that may requiresuch surface modification include aluminum, steel, iron, copper, nickel,gold, silicon, and nonfunctionalized polymers. In the area of sensing ofcomponents, degradants, and impurities in foodstuffs, solid supportmaterials include polyethylenes such as LDPE and ULLDPE, EVA and others.In addition to solid surface immobilization through covalentinteractions, noncovalent interactions (such as that of biotin withstreptavidin, for example), as well as other similar chemistries thatare well-known to those of skill in the art are applicable in thepresent invention. Example 43 describes the ability of a surface boundsensing compound to detect fluoride ion.

[0069] While the above examples recite solid support immobilization viacovalent interactions, binding moieties may also include functionalgroups that attach to the solid support via a high-affinity, noncovalentinteraction (such as biotin with streptavidin), as well as other meansthat are well-known to those of skill in the art.

[0070] The selective binding capabilities of the sensing elementsdescribed herein may be useful in a number of applications wherein itwill be advantageous to have such binding on a solid support. Forexample, binding to silica-based supports would have utility in theseparation sciences. These have additional utility in the area of fiberoptic sensing. Functionalization of the sensing clement with silylalcohols groups, among others, will allows for attachment onto silica.Additionally, it will be beneficial for similar purposes to incorporatesuch sensing elements onto a polymer support. The molecule shown atright in the example below may be incorporated into a polymerizingchemistry known to one of skill in the art to afford a material that hasthe ability to behave as a sponge toward analytes of interest.

[0071] In the above example, R₁-R₃ is hydrogen, alkyl, hydroxyalkyl,glycol, polyglycol, amino, nitro, halo, cyano, aryl, heteroaryl, thio,thioalkyl, amide, ester, acyl, aldehyde, or carboxy.

Enhancement of Water Solubility

[0072] The unsubstituted pyrrole-aryls have relatively low solubility.In order to enhance further the general utility of these species assensing compounds, it is desirable to afford one the capability ofreadily enhancing water solubility. Such solubility characteristics maybe tailored through functionalzation. Water solubility is most markedlyenhanced through the functionalization of these sensing compounds withgroups that readily carry a formal charge in aqueous solutions.Additionally, groups of varying polarity may be used to modify watersolubility. Combinations of these groups can be used depending upon thelevel of water solubility sought to be imparted to the sensing compound.

[0073] Functional groups which find applicability in this regard includecarboxy, amino, sulfonate, alcohols. Oxyhydroxyalkyl and oxycarboxygroups such a hydroxypropoxy and carboxyethoxy are useful in thisregard. Multiply carboxylated derivatives may be used in their nativeform or they may be converted to ester or amide products that can beused to further append hydroxylated substituents. Polyether-linkedpolyhydroxylated alkyl groups, polyethylene glycols and othermulti-hydroxy containing groups will also afford enhanced watersolubility while allowing the sensing element to retain lipophilicity.

Pharmaceutical Compositions and Routes of Administration

[0074] Apart from the application of the subject sensing elements as invivo and in vitro sensors, it is envisioned that they may be used astherapeutic agents. They are particularly useful in applications wereanion and neutral molecule transport are necessary. One specific exampleinvolves the use of chloride ion transport for the treatment of cysticfibrosis. Cystic fibrosis is a hereditary disease characterized by theproduction of defective chloride channel proteins in epithelial cells,particularly the lungs. Established treatments target the symptoms ofthe disease but do not compensate for the poor chloride ion transport.An effective, biocompatible carrier that functions in vivo to augmentcell permeability for chloride anion could provide a conceptuallysimple, potentially new approach to cystic fibrosis treatment. Thesesensing elements have therapeutic uses in any situation wherein theselective transport of an anion or neutral species is desired. Onevariation on the class of compounds described herein involves thederivatization with crown ethers. Such compounds would enhance the roleof ion or neutral species transport.

[0075] Where clinical application of controlled release compositions isundertaken, it will be necessary to prepare the composition as apharmaceutical composition appropriate for the intended application.Generally, this will entail preparing a sterile, physiologicallycompatible pharmaceutical composition that is essentially free ofpathogens, as well as any other impurities that could be harmful tohumans or animals. One also will generally desire to employ appropriatebuffers to render the complex stable and allow for uptake by targetcells.

[0076] Aqueous compositions of the present invention comprise aneffective amount of a controlled release composition as discussed abovedispersed in a pharmaceutically acceptable carrier or aqueous medium.Such compositions also are referred to as inocula. The phrases“pharmaceutically” or “pharmacologically acceptable” refer tocompositions that do not produce an adverse, allergic or other untowardreaction when administered to an animal, or a human, as appropriate.

[0077] As used herein, “pharmaceutically acceptable carrier” includesany and all solvents, dispersion media, coatings, antibacterial andantifungal agents, isotonic and absorption delaying agents and the like.The use of such media and agents for pharmaceutical active substances iswell known in the art. Except insofar as any conventional media or agentis incompatible with the active ingredient, its use in the therapeuticcompositions is contemplated. Supplementary active ingredients also canbe incorporated into the compositions.

[0078] Solutions of therapeutic compositions can be prepared in watersuitably mixed with a surfactant, such as hydroxypropylcellulose.Dispersions also can be prepared in glycerol, liquid polyethyleneglycols, mixtures thereof and in oils. Under ordinary conditions ofstorage and use, these preparations contain a preservative to preventthe growth of microorganisms.

[0079] The therapeutic compositions of the present invention areadvantageously administered in the form of injectable compositionseither as liquid solutions or suspensions; solid forms suitable forsolution in, or suspension in, liquid prior to injection may also beprepared. These preparations also may be emulsified. A typicalcomposition for such purpose comprises a pharmaceutically acceptablecarrier. For instance, the composition may contain 10 mg, 25 mg, 50 mgor up to about 100 mg of human serum albumin per milliliter of phosphatebuffered saline. Other pharmaceutically acceptable carriers includeaqueous solutions, non-toxic excipients, including salts, preservatives,buffers and the like.

[0080] Examples of non-aqueous solvents are propylene glycol,polyethylene glycol, vegetable oil and injectable organic esters such asethyl oleate. Aqueous carriers include water, alcoholic/aqueoussolutions, saline solutions, parenteral vehicles such as sodiumchloride, Ringer's dextrose, etc. Intravenous vehicles include fluid andnutrient replenishers. Preservatives include antimicrobial agents,anti-oxidants, chelating agents and inert gases. The pH and exactconcentration of the various components in the pharmaceuticalcomposition are adjusted according to well known parameters.

[0081] Additional formulations are suitable for oral administration.Oral formulations include such typical excipients as, for example,pharmaceutical grades of mannitol, lactose, starch, magnesium stearate,sodium saccharine, cellulose, magnesium carbonate and the like. Thecompositions take the form of solutions, suspensions, tablets, pills,capsules, sustained release formulations or powders. When the route istopical, the form may be a cream, ointment, salve or spray.

[0082] The therapeutic compositions of the present invention may includeclassic pharmaceutical preparations. Administration of therapeuticcompositions according to the present invention will be via any commonroute so long as the target tissue is available via that route. Thisincludes oral, nasal, buccal, rectal, vaginal or topical. Topicaladministration would be particularly advantageous for the treatment ofskin cancers, to prevent chemotherapy-induced alopecia or other dermalhyperproliferative disorder. Alternatively, administration may be byorthotopic, intradermal subcutaneous, intramuscular, intraperitoneal orintravenous injection. Such compositions would normally be administeredas pharmaceutically acceptable compositions that include physiologicallyacceptable carriers, buffers or other excipients. For treatment ofconditions of the lungs, the preferred route is aerosol delivery to thelung. Volume of the aerosol is between about 0.01 ml and 0.5 ml.Similarly, a preferred method for treatment of colon-associated diseasewould be via enema. Volume of the enema is between about 1 ml and 100ml.

[0083] An effective amount of the therapeutic composition is determinedbased on the intended goal. The term “unit dose” or “dosage” refers tophysically discrete units suitable for use in a subject, each unitcontaining a predetermined-quantity of the therapeutic compositioncalculated to produce the desired responses, discussed above, inassociation with its administration, i.e., the appropriate route andtreatment regimen. The quantity to be administered, both according tonumber of treatments and unit dose, depends on the protection desired.

[0084] Precise amounts of the therapeutic composition also depend on thejudgment of the practitioner and are peculiar to each individual.Factors affecting the dose include the physical and clinical state ofthe patient, the route of administration, the intended goal of treatment(alleviation of symptoms versus cure) and the potency, stability andtoxicity of the particular therapeutic substance. Example 42 discussesanion binding compounds as therapeutic agents.

[0085] The following examples are included to demonstrate preferredembodiments of the invention. It should be appreciated by those of skillin the art that the techniques disclosed in the examples which followrepresent techniques discovered by the inventor to function well in thepractice of the invention, and thus can be considered to constitutepreferred modes for its practice. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments which are disclosed and stillobtain a like or similar result without departing from the spirit andscope of the invention.

[0086] The following examples are merely illustrative and notexhaustive. Examples of compositions useful in the present invention,along with their preparation are given. It is expected that one skilledin the art may appreciate that minor deviations may be incorporatedwithout deviating from the scope of the present invention.

EXAMPLE 1 Synthesis of 1,2-Dipyrryl ethanedione

[0087] Oxalyl chloride (6.4 g, 0.05 mol) and dichloromethane (25 mL)were placed together under an argon atmosphere and stirred. Upon coolingto −78° C. in an acetone/CO₂ bath, dry pyridine (10 g, 0.12 mol) wasadded, resulting in the formation of a yellow precipitate. To thiscooled suspension was added a solution of freshly distilled pyrrole (6.7g, 0.1 mol) in dichloromethane (25 mL) by use of a canula. Immediately,the reaction mixture turns from yellow to brown. The reaction wasallowed to stir for an additional 15 minutes at −60° C., after whichtime hydrochloric acid (5 M, 100 mL) was added to quench the reaction.The biphasic system is then separated and the organic phase wascollected. The aqueous phase was extracted with dichloromethane (3×30mL), and the combined organic phases were washed with water (100 mL),dried over anhydrous sodium sulfate, filtered and evaporated to dryness.This afforded a green precipitate. The crude product was furtherpurified by silica gel column chromatography (acetone/hexanes (80/20v/v)) to afford 10 (1.81g, 38%) as a yellow powder.

Chracterization Data for 10

[0088] 1H NMR (250 MHz, DMSO d₆) δ6.26 (2H, dd, J₁=3.7 Hz, J₂=2.4 Hz,H_(β)), 6.89 (2H, dd, J₁=3.7 Hz, J₂=0.5 Hz, H_(βpyrr)), 7.30 (broad s,H_(αpyrr)), 12.27 (2H, s, NH); ¹³C NMR (125 MHz, DMSO d₆) δ111.0, 120.9,128.4, 128.6, 181.4.

EXAMPLE 2 Synthesis of 2,3-dypyrrylquinoxaline (1)

[0089] The synthesis of 2,3-dipyrrylquinoxaline (1) was carried out asfollows. The diketone 10 (570 mg, 3.03 mmol) was dissolved in glacialacetic acid (70 mL) and to this was added a solution ofortho-phenylenediamine (715 mg, 6.62 mmol) in acetic acid (30 mL) withstirring. The resultant mixture was then brought to reflux for 90 minunder an atmosphere of argon. After this time majority of the aceticacid was removed under vacuum and the residue was taken up in a mixtureof water (30 mL) and dichloromethane (30 mL). The organic phase wasseparated off and the aqueous phase was extracted with furtherdichloromethane (2×20 mL). The organic phases were combined and washedwith saturated aqueous sodium bicarbonate solution (50 mL), water and(50 mL) and brine (50 mL). After drying over anhydrous sodium sulfate,filtered and evaporated to dryness. The residue obtained was thepurified using silica gel column chromatography (dichloromethane) toafford 1 (730 mg, 94%) as a yellow powder.

[0090] Oxalyl chloride, o-phenylenediamine, 4-nitro-1,2-diaminobenzenewere purchased from Aldrich and used without further purification.4,5-Diamino-1,2-dimethoxybenzene was prepared according to the method ofSessler, 1992. 4-5,-Dinitro-1,2-diaminobenzene was prepared according tothe method of Cheeseman, 1962.

Characterization Data for 1:

[0091]¹H NMR (250 MHz, CDCl₃) δ6.16 (2H, m, H_(β2)), 6.82 (2H, m,H_(β1)), 6.89 (2H, m, H_(α)), 7.46 (2H, dd, J_(o)=12.5 Hz, J_(m)=2.9 Hz,CH_(benz)), 7.78 (2H, dd, J_(o)=12.5 Hz, J_(m)=2.9 Hz, CH_(benz)), 9.54(2H, broad s, NH); ¹³C NMR (125 MHz, CDCl₃) δ109.9, 112.8, 121.1, 128.0,128.8, 129.0, 139.6, 143.6; HRMS (CI+) m/z calcd for C₁₆H₁₃N₄:261.11402, found: 261.11343; Anal. Calcd for C₁₆H₁₃N₄.0.5H₂O: C, 71.35;H, 4.87; N, 20.80. Found C, 71.23; H, 4.79; N, 20.48.

EXAMPLE 3 Synthesis of 2,3-dipyrrol-2′-yl-6,7-dimethoxyquinoxaline (2)

[0092] 4,5-Diamino-1,2-dimethoxybenzene (1.25 g, 7.45 mmol) and1,2-dipyrrol-2′-ylethanedione (2 g, 10.65 mmol) were dissolved in aceticacid (250 mL) and heated at reflux under an atmosphere of argonovernight. The solvent was removed under vacuum and the residue wastaken up in a mixture of water (50 mL) and dichloromethane (100 mL). Theorganic phase was separated off and the aqueous phase was extracted withfurther dichloromethane (2×40 mL). The organic phases were combined andwashed with saturated aqueous sodium bicarbonate solution (50 mL), water(50 mL), then brine (50 mL). After drying over anhydrous sodium sulfate,the solution was filtered and evaporated to dryness. Final purificationwas then effected using silica gel column chromatography(methanol/chloroform, 2:98) to afford2,3-dipyrrol-2′-yl-6,7-dimethoxyquinoxaline (2.05 g, 86%) as ayellow/green powder: m.p. 196-198° C.; ¹H NMR (250 MHz, DMSO d6) δ3.98(6H, s), 6.05-6.09 (2H, m), 6.11-6.15 (2H, m), 6.92-6.96 (2H, m), 7.32(2H, s), 11.35 (2H, br s, NH); ¹³C NMR (62.5 MHz, CDCl₃) δ56.7, 106.5,110.4, 112.1, 120.8, 129.7, 137.3, 142.3, 152.7; HRMS (CI+) m/z (M+1)calcd. for C₁₈H₁₇N₄O₂: 321.1352, found: 321.1358; UV-vis (CH₂CI₂)λ_(max) [nm] (ε): 272 (23 890), 292sh (17 850), 412 (15 900).

Characterization Data for 2

[0093] m.p. 196-198° C.; ¹H NMR (250 MHz, DMSO d₆) δ3.98 (6H, s),6.05-6.09 (2H, m), 6.11-6.15 (2H, m), 6.92-6.96 (2H, m), 7.32 (2H, s),11.35 (2H, br, s, NH); ¹³C NMR (125 MHz, CDCl₃) δ56.7, 106.5, 110.4,112.1, 120.8, 129.7, 137.3, 142.3, 152.7; HRMS (CI+) m/z (M+1) calcd.for C₁₈H₁₇N₄O₂: 321.1352, found: 321.1358.

EXAMPLE 4 Synthesis of 2,3-dipyrrol-2′-yl-6,7-dinitroquinoxaline (3)

[0094] 1,2-Dipyrrol-2′-ylethanedione (200 mg, 1.06 mmol) and1,2-diamino-4,5-dinitrobenzene (265 mg, 1.34 mmol) were dissolved inglacial acetic acid (40 mL) and the resultant solution was heated atreflux in the dark for 4 h under an atmosphere of argon. The solutionwas allowed to cool and evaporated to dryness in vaccuo. The residue wastaken up in dichloromethane (50 mL) and washed with sodium hydrogencarbonate solution (sat., 2×50 mL), brine (50 mL), dried over anhydroussodium sulfate, filtered and evaporated to dryness. The residue waschromatographed over silica (chloroform) and the front running band wascollected to afford 2,3-dipyrrol-2′-yl-6,7-dinitroquinoxaline (297 mg,80%) as a red powder: m.p. 215-217° C.; 1H NMR (250 MHz, DMSO d₆)δ6.20-6.28 (2H, m, pyrrole H), 6.68-6.77 (2H, m, pyrrole H), 7.15-7.22(2H, m, pyrrole H), 8.50 (2H, s, quinoxline H), 11.94 (2H, br s, NH);¹³C NMR (62.5 MHz, DMSO d₆) δ109.9, 114.9, 124.6, 125.7, 127.9, 140.0,140.7, 147.7; HRMS (CI+) m/z (M+1) calcd. for C₁₆H₁₁N₆O₄ 351.0842, found351.0852; UV-vis (CH₂Cl₂) λ_(max) [nm] (ε): 340 (29 100), 460 (29 200).

EXAMPLE 5 Synthesis of 6-nitro-2-3-dipyrrylquinoxaline (7)

[0095] 1,2-Dipyrrol-2′-ylethanedione (175 mg, 0.93 mmol) and4-nitro-1,2-diaminobenzene (245 mg, 1.60 mmol) were dissolved in glacialacetic acid (30 mL) and the resultant solution was heated at reflux inthe dark overnight under an atmosphere of argon. The solution wasallowed to cool and evaporated to dryness in vaccuo. The residue wastaken up in dichloromethane (50 mL) and washed with sodium hydrogencarbonate solution (sat., 2×50 mL), brine (50 mL), dried over anhydroussodium sulfate, filtered and evaporated to dryness. The residue waschromatographed over silica (chloroform) and the front running band wascollected to afford 2,3-dipyrrol-2′-yl-6-nitroquinoxaline (240 mg, 85%)as a red powder: m.p. 206-208° C.; ¹H NMR (250 MHz, DMSO d₆) δ6.15-6.25(2H, m, pyrrole H), 6.45-6.60 (2H, m, pyrrole H), 7.07-7.19 (2H, m,pyrrole H), 8.05 (1H, d, J 9.1 Hz, H8 quinoxaline), 8.48 (1H, dd, J 9.1,2.5 Hz, H7 quinoxaline), 8.65 (1H, d, J 2.5 Hz, H5 quinoxaline), 11.75(1H, br s, NH), 11.86 (1H, br s, NH); ¹³C NMR (62.5 MHz, DMSO d₆)δ109.2, 109.6, 112.9, 114.1, 122.3, 122.6, 123.6, 123.7, 128.1, 128.3,129.2, 137.8, 142.4, 146.3, 146.5, 147.0; HRMS (CI+) m/z (M+1) Calcd forC₁₆H₁₂N₅O₂ 306.0991, found 306.0996; UV-vis (CH₂Cl₂) λ_(max) [nm] (ε):325 (22 000), 370 (13 650), 450 (18 730); Anal. Calc. for C₁₆H₁₁N₅O₂: C,62.95; H, 3.61; N, 22.95. Found C, 62.87; H, 3.67; N, 22.96.

EXAMPLE 6 Synthesis of Mono-2-(trimethylsilyl)ethoxymethyl (SEM)protected derivative (12).

[0096] 2,3-Dipyrrylquinoxaline (400 mg, 1.54 mmol) was dissolved inN,N-dimethylformamide (30 ml) under an atmosphere of argon. Sodiumhydride (60% dispersion in mineral oil, 100 mg) was added and theresultant mixture was allowed to stir at room temperature for 1 h.2-(trimethylsilyl)ethoxymethyl chloride (SEM-Cl) (205 mg, 1.23 mmol) wasthen added and the mixture was stirred at room temperature for a further90 min. The solvent was removed under vacuum and the residue was takenup in dichloromethane (150 ml) and washed with water (2×100 ml), andbrine (100 ml). The organic phase was dried over sodium sulfate,filtered and evaporated to dryness. Final purification was then effectedusing silica gel column chromatography (toluene initially, thentoluene/ethylacetate, 95/5) to afford 7 (40 mg, 6.6%) as a brown gum: ¹HNMR (500 MHz, CD₂Cl₂) δ−0.70 (9H, s), 0.56-0.60 (2H, m), 3.23-3.27 (2H,m), 5.15 (2H, s), 5.78-5.80 (1H, m), 6.12-6.14 (1H, m), 6.34-6.37 (1H,m), 6.48-6.51 (1H, m), 6.96-6.98 (1H, m), 7.02-7.04 (1H, m), 7.63-7.67(1H, m), 7.71-7.75 (1H, m), 7.98-7.82 (1H, m), 9.90-10.00 (1H, br s);¹³C NMR (125 MHz, CD₂Cl₂) δ−1.6, 17.8, 30.1, 66.1, 77.0, 109.0, 111.0,112.3, 113.1, 122.0, 123.4, 128.4, 128.8, 129.4, 130.6, 140.4, 141.2,145.3, 146.0.

EXAMPLE 7 Preparation of 2,3-di-5′-bromopyrrol-2′-ylquinoxaline

[0097] 2,3-Dipyrrol-2′-ylquinoxaline (1.5 g, 5.77 mmol) was dissolved incarbon tetrachloride (150 ml) and recrystallised N-bromosuccinimde (2.25mg, 12.64 mmol) and benzoyl peroxide (40 mg) were added and theresultant mixture was heated at reflux under an atmosphere of argon inthe dark overnight. The solvent was then removed under vacuum and theresidue was chromatographed over silica (ethyl acetate/dichloromethane5:95) and the major band was collected to afford2,3-di-5′-bromopyrrol-2′-ylquinoxaline (1.7 g, 70%) as a light brownsolid: m.p. 204-206° C.; ¹H NMR (250 MHz, DMSO d₆) δ6.16-6.24 (4H, m,β-pyrrolic H), 7.73-7.81 (2H, m, aryl H), 7.95-8.03 (2H, m, aryl H),12.3 (2H, broad s, NH); ¹³C NMR (62.5 MHz, DMSO d₆) δ101.9, 111.1,112.8, 128.1, 129.6, 130.4, 139.5, 143.9; HRMS (CI+) m/z calcd forC₁₆H₁₁N₄Br₂: 416.93504, found: 416.93557; Anal. Calcd for C₁₆H₁₀N₄Br₂:C, 45.93; H, 2.39; N, 13.40. Found C, 46.09; H, 2.56; N, 13.49.

EXAMPLE 8 Preparation of 2,3-di-5′-iodopyrrol-2′-ylquinoxaline

[0098] 2,3-Dipyrrol-2′-ylquinoxaline (500 mg, 1.92 mmol) and sodiumacetate (1.04 g, 7.68 mmol) were dissolved in acetic acid (100 mL) andcooled to 0° C. in an ice bath. As the acetic acid began to crystallise,a solution of iodine monochloride (592 mg, 3.65 mmol) in acetic acid (10mL) was added to the quinoxaline solution and the mixture was stirredfor 10 min. A saturated solution of sodium thiosulfate (30 mL) was thenadded and the mixture was stirred at room temperature for 1 h. Themixture was then washed with ethyl acetate (100 mL) and the organicphase was separated off. The organic phase was washed with water (2×100mL) and brine (100 mL), dried over anhydrous sodium sulfate, filteredand evaporated to dryness. The residue ws achromatographed over silica(dichloromethane/hexane 1:1, v/v) to afford2,3-di-5′-iodopyrrol-2′-ylquinoxaline (830 mg, 84%).

EXAMPLE 9 Preparation of 2,3-di(5′-formylpyrrol-2′-yl)quinoxaline

[0099] Phosphorus oxychloride (240 μL, 2.57 mmol) was added to DMF (454μL, 5.86 mmol) at 0° C. under an atmosphere of argon. This mixture wasthen allowed to warm to room temperature and stirred for 10 min before1,2-dichloroethane (3 mL) was added. To this mixture was then added asolution of 2,3-dipyrrol-2′-ylquinoxaline (260 mg, 1.00 mmol) in1,2-dichloroethane (3 mL) over a period of 10 min. The resulting mixturewas heated at reflux for 30 min before being cooled to 0° C. A saturatedaqueous solution of sodium acetate (3 mL) was then added and the mixturewas heated at reflux for a further 30 min. Upon cooling, the mixture waswashed with chloroform (2×50 mL) and the combined organic phases werethen washed with water (2×50 mL), brine (50 mL), dried over anhydroussodium sulfate, filtered and evaporated to dryness. The residue was thenchromatographed over silica (dichloromethane initially, thendichloromethane/methanol, 99.5:0.5 v/v) to afford2,3-di(5′-formylpyrrol-2′-yl)quinoxaline (216 mg, 68%) as a yellowsolid.

EXAMPLE 10 Preparation of 2,3-di(5′-benzoylpyrrol-2′-yl)quinoxaline

[0100] Under an atmosphere of argon, NN-dimethylbenzamide (1.20 g, 8.0mmol) was added to 1,2-dichloroethane (5 mL) followed by the addition ofphosphorus oxychloride (368 μL, 3.96 mmol) and and the mixture wasstirred at room temperature for 30 min. To this mixture was added asolution of 2,3-dipyrrol-2′-ylquinoxaline (400 mg, 1.54 mmol) in1,2-dichloroethane (50 mL) over a period of 20 min. The resultingmixture was heated at reflux for 24 h before being allowed to cool. Anaqueous solution of sodium acetate (20 mL) was then added and themixture was heated at reflux for a further 30 min. Upon cooling, themixture was washed with dichloromethane (2×100 mL) and the combinedorganic phases were then washed with water (2×150 mL), brine (150 mL),dried over anhydrous sodium sulfate, filtered and evaporated to dryness.The residue was then chromatographed over silica (dichloromethane) toafford 2,3-di(5′-benzoylpyrrol-2′-yl)quinoxaline (314 mg, 44%).

EXAMPLE 11 Preparation of 2,3-dipyrrol-2′-yl-6,7-dipentoxyquinoxaline

[0101] 4,5-Dipentoxy-1,2-diaminobenzene (1.12 g, 4.0 mmol) and1,2-dipyrrol-2′-ylethanedione (500 mg, 2.66 mmol) were dissolved inacetic acid (80 ml) and the resulting mixture was first evacuated, andthen placed under an atmosphere of argon and heated at reflux in thedark overnight. The mixture was allowed to cool and the solvent wasremoved under vacuum. The residue was then dissolved in dichlormethane(100 ml) and washed with sodium carbonate solution (100 ml), brine (100ml), dried over anhydrous sodium sulfate and evaporated to dryness. Theresidue was then chromatographed over silica (dichloromethane) and thefront running band was collected to afford2,3-dipyrrol-2′-yl-6,7-dipentoxyquinoxaline (768 mg, 67%) as ayellow-green powder: m.p. 142-144° C.; ¹H NMR (250 MHz, DMSO d₆) δ0.94(6H, t, J 7.0 Hz, CH₃), 1.33-1.56 (8H, m, γ and δ CH₂), 1.84 (4H, appquin., β CH₂), 4.17 (4H, t, J 6.3 Hz, α CH₂), 6.03-6.08 (2H, m, pyrroleH), 6.09-6.14 (2H, m, pyrrole H), 6.90-6.95 (2H, m, pyrrole H), 7.25(2H, s, quinoxaline H), 11.38 (2H, br s, NH); ¹³C NMR (62.5 MHz, DMSOd₆) δ13.9, 21.9, 27.8, 28.1, 68.4, 106.8, 108.6, 110.1, 120.2, 128.9,151.4; HRMS (CI+) m/z (M+1) calcd. for C₂₆H₃₃N₄O₂ 433.2603, found433.2613.

EXAMPLE 12 Preparation of2,3-di(5′-bromopyrrol-2′-yl)-6-nitroquinoxaline

[0102] 2,3-Dipyrrol-2′-yl-6-nitroquinoxaline (500 mg, 1.64 mmol) wasdissolved in carbon tetrachloride (150 mL) and recrystallised NBS (613mg, 3.44 mmol, 2.1 equiv.) and benzoyl peroxide (10 mg) were added. Theresultant mixture was heated at reflux under an atmosphere of argon inthe dark overnight. The mixture was allowed to cool and then evaporatedto dryess. The residue was chrommatographed over silica(dichloromethane) to afford2,3-di(5′-bromopyrrol-2′-yl)-6-nitroquinoxaline (226 mg, 30%) as a redsolid.

EXAMPLE 13 Preparation of 2,3-dipyrrol-2′-yl-6-aminoquinoxaline

[0103] 2,3-Dipyrrol-2′-yl-6-nitroquinoxaline (107 mg, 0.35 mmol) wasdissolved in ethanol (20 mL) and palladium on carbon (10%, 10 mg) wasadded. The mixture was placed under an atmosphere of hydrogen andstirred overnight in the dark. The mixture was then filtered throughcelite and the filtrate was evaporated to dryness to afford2,3-dipyrrol-2′-yl-6-aminoquinoxaline (90 mg, 93 %) as an orange solid.

EXAMPLE 14 Preparation of 2,3-dipyrrol-2′-yl-6,7-diaminoquinoxaline

[0104] 2,3-Dipyrrol-2′-yl-6,7-dinitroquinoxaline (90 mg, 0.25 mmol) wasdissolved in absolute ethanol (40 mL) and 10% palladium on carbon (15mg) was added. The resulting mixture was stirred under an atmosphere ofhydrogen overnight in the dark. The solution was then filtered throughcelite and evaporated to dryness to afford crude2,3-dipyrrol-2′-yl-6,7-diaminoquinoxaline (72 mg, 100%) and used withoutfurther purification.

EXAMPLE 15 Preparation of 2,3-dipyrrol-2′-yl-5-nitroquinoxaline

[0105] 1,2-Dipyrrol-2′-ylethanedione (500 mg, 2.66 mmol) and3-nitro-1,2-phenylenediamine (680 mg, 4.45 mmol) were dissolved inacetic acid (100 mL) and heated at reflux in the dark under anatmosphere of argon overnight. The solvent was removed under vacuum andthe residue was dissolved in dichloromethane (150 mL), washed withsodium carbonate solution (2×100 mL) and brine (100 mL), dried overanhydrous sodium sulfate, filtered and evaporated to dryness. The crudematerial was then chromatographed over silica (dichloromethane) and themajor front running band was collected to afford2,3-dipyrrol-2′-yl-5-nitroquinoxaline (480 mg, 59%) as an orange solid:m.p. 183-185° C.; ¹H NMR (250 MHz, DMSO d₆) δ6.15-6.22 (2H, m, pyrroleH), 6.39-6.47 (2H, m, pyrrole H), 7.05-7.10 (2H, m, pyrrole H),7.76-7.84 (1H, m, quinoxaline H), 8.14-8.22 (2H, m, quinoxaline H),11.41 (1H, br s, NH), 11.77 (1H, br s, NH); ¹³C NMR (62.5 MHz, DMSO d₆)δ109.3, 113.0, 113.4, 122.7, 123.0, 123.2, 0127.6, 128.0, 128.1, 131.0,131.9, 139.3, 145.9, 146.2; HRMS (CI+) m/z (M+1) Calcd for Cl₆H₁₂N₅O₂306.0991, found 306.0995.

EXAMPLE 16 Preparation of 2,3-dipyrrol-2′-yl-6-bromoquinoxaline

[0106] 1,2-Dipyrrol-2′-ylethanedione (440 mg, 2.34 mmol) and4-bromo-1,2-phenylenediamine (560 mg, 3.00 mmol) were dissolved inacetic acid (70 mL) and heated at reflux in the dark under an atmosphereof argon overnight. The solvent was removed under vacuum and the residuewas dissolved in dichloromethane (150 mL), washed with sodium carbonatesolution (2×100 mL) and brine (100 mL), dried over anhydrous sodiumsulfate, filtered and evaporated to dryness. The crude material was thenchromatographed over silica (dichloromethane) and the major frontrunning band was collected to afford2,3-dipyrrol-2′-yl-6-bromoquinoxaline (510 mg, 65%) as a brown/greensolid: m.p. 144-146° C.; ¹H NMR (500 MHz, DMSO d6) δ6.12-6.15 (2H, m,pyrrole H), 6.28-6.30 (2H, m, pyrrole H), 6.98-7.02 (2H, m, pyrrole H),7.80 (1H, dd, J 2.1, J 8.8 Hz, quinoxaline H), 7.85 (1H, d, J 8.8 Hz,quinoxaline H), 8.07 (1H, d, J 2.1 Hz, quinoxaline H), 11.57 (2H, br s,NH); ¹³C NMR (125 MHz, DMSO d₆) δ108.9, 109.1, 112.0, 112.2, 121.5,121.8, 122.0, 128.3, 128.4, 129.1, 130.0, 132.0, 138.2, 140.1, 145.3,145.7; MS (CI+) m/z (M+1) Calcd for C₁₆H₁₂N₄Br 339.02453, found339.02430.

EXAMPLE 17 Preparation of 2,3-diaminonaphthalene adduct

[0107] 1,2-Dipyrrol-2′-yl ethanedione (200 mg, 1.06 mmol) and2,3-diaminonaphthalene (252 mg, 1.59 mmol) were dissolved in glacialacetic acid (30 mL) and the resultant solution was heated at refluxunder an atmosphere of argon in the dark overnight. The solution wasallowed to cool and evaporated to dryness in vaccuo. The residue wastaken up in dichloromethane (50 mL) and washed with sodium hydrogencarbonate solution (sat., 2×50 mL), brine (50 mL), dried over anhydroussodium sulfate, filtered and evaporated to dryness. The residue waschromatographed over silica (dichloromethane) and the front running bandwas collected to afford the 2,3-diaminonaphthalene adduct (156 mg, 95%)as a light brown solid: m.p. 184-186° C.; ¹H NMR (250 MHz, DMSO d₆)δ6.15-6.20 (2H, m, pyrrole H), 6.34-6.39 (2H, m, pyrrole H), 7.03-7.08(2H, m, pyrrole H), 7.55-7.64 (2H, m), 8.15-8.23 (2H, m), 8.54 (2H, s),11.71 (2H, br s, NH); ¹³C NMR (62.5 MHz, DMSO d₆) δ108.9, 112.6, 122.0,125.6, 126.3, 128.2, 129.0, 133.0, 136.7, 145.8; HRMS (CI+) m/z (M+1)Calcd for C₂₀H₁₅N₄ 311.12967, found 311.12963.

EXAMPLE 18 Preparation of 9,10-diaminophenanthrene adduct

[0108] 1,2-Dipyrrol-2′-yl ethanedione (500 mg, 2.66 mmol) and9,10-diaminophenanthrene (830 mg, 3.99 mmol) were dissolved in glacialacetic acid (150 mL) and the resultant mixture was heated at refluxunder an atmosphere of argon in the dark overnight. The mixture wasallowed to cool and evaporated to dryness in vaccuo. The residue waschromatographed over silica (diclhoromethane) and the front running bandwas collected to afford the 9,10-diaminophenanthrene adduct (687 mg,72%) as a light brown solid. HRMS (CI+) m/z (M+1) Calcd for C₂₄H₁₇N₄361.14532, found 361.14525.

EXAMPLE 19 Preparation of 2,3-dipyrrol-2′-yl-6-carboxyquinoxaline

[0109] 1,2-Dipyrrol-2′-ylethanedione (500 mg, 2.66 mmol) and3,4-diaminobenzoic acid (404 mg, 2.66 mmol) were dissolved in glacialacetic acid (80 mL) and the resultant solution was heated at reflux inthe dark overnight. The solution was allowed to cool and evaporated todryness in vaccuo. The residue was taken up in ethyl acetate (150 mL)and washed with hydrochloric acid (3 M, 80 mL), brine (80 mL), driedover anhydrous sodium sulfate, filtered and evaporated to dryness. Theresidue was chromatographed over silica (ethyl acetate/dichloromethane,3:2 v/v) and the major band was collected to afford2,3-dipyrrol-2′-yl-6-carboxyquinoxaline (270 mg, 33%). ¹H NMR (250 MHz,DMSO d₆) δ6.14-6.21 (2H, m, pyrrole H), 6.35-6.43 (2H, m, pyrrole H),7.02-7.09 (2H, m, pyrrole H), 8.00 (1H, d, J 8.7 Hz, H8 quinoxaline),8.17 (1H, dd, J 8.7, 1.9 Hz, H7 quinoxaline), 8.49 (1H, d, J 2.5 Hz, H5quinoxaline), 11.66 (1H, br s, NH), 11.73 (1H, br s, NH), 13.40 (1H, brs, CO₂H); ¹³C NMR (62.5 MHz, DMSO d₆) δ109.0, 109.3, 112.1, 112.8,121.8, 122.5, 128.1, 128.4, 128.5, 129.9, 130.6, 138.5, 141.5, 145.8,146.3, 166.8; HRMS (CI+) m/z (M+1) Calcd for C₁₇H₁₃N₄O₂ 305.1039, found305.1035.

EXAMPLE 20 Preparation of 2,3-dipyrrol-2′-yl-6-carboxyquinoxalineoctylester

[0110] 2,3-Dipyrrol-2′-yl-6-carboxyquinoxaline (100 mg, 0.33 mmol) andoctanol (47 mg, 0.36 mmol) were dissolved in dichloromethane (20 mL). Tothis solution was added DCC (82 mg, 0.40 mmol) and DMAP (2.5 mg, 0.02mg)in dichloromethane (10 mL) over a 10 min period and the resultingmixture was stirred at room temperature for 4 h. The mixture was thenevaporated to dryness and chromographed over silica (dichloromethane) toafford 2,3-dipyrrol-2′-yl-6-carboxyquinoxaline octyl ester (76 mg, 55%)as a yellow/green solid.

EXAMPLE 21 Preparation of2,3-dipyrrol-2′-yl-6-carbxyamidoaquinoxaline-4″-benzo-18-crown-6

[0111] 2,3-Dipyrrol-2′-yl-6-carboxyquinoxaline (100 mg, 0.33 mmol) wasdissolved in a mixture of dichloromethane (10 mL) andN,N-diisopropylethylamine (100 mg, 0.724 mmol) and HBTU (137 mg, 0.362mmol) was added. The resulting mixture was stirred for 5 min prior tothe addition of a solution of 4-aminobenzo-18-crown-6 (118 mg, 0.36mmol) in dichloromethane (6 mL). The reaction mixture was allowed tostir under an atmosphere of argon in the dark overnight. The mixture wasthen evaporated to dryness and the residue was chromatographed oversilica (ethyl acetate initially, then methanol/ethyl acetate, 5:95 v/v)to afford2,3-dipyrrol-2′-yl-6-carbxyamidoaquinoxaline-4″-benzo-18-crown-6 (150mg, 74%).

EXAMPLE 22 Preparation of 2,3-dipyrrol-2′-yl-6-carboxyquinoxalinecoupled to a bead

[0112] 2,3-Dipyrrol-2′-yl-6-carboxyquinoxaline (45 mg, 0.14 mmol), HBTU(62 mg, 0.16 mmol), N,N-diisopropylethylamine (50 mg, 0.36 mmol) and DMF(0.5 mL) were added to dichloromethane (7 mL). This solution was thenadded to pre-swelled TG-amino resin (the resin was successively rinsedwith DMF, then dichloromethane and then methanol several times). Themixture was stirred overnight and then filtered under vacuum and washedsuccessively with dichoromethane, DMF, dichoromethane, DMF,dichloromethane, methanol, dichloromethane, and finally two rinses withmethanol. After the third wash the solutions were colourless. The beadswere then dried under vacuum for 4 days without further purification.

EXAMPLE 23 1,2-Di(3′,4′-difluoropyrrol-2′-yl)ethanedione

[0113] Oxalyl chloride (800 μL, 8.64 mmol) and dichloromethane (15 mL)were placed together under an argon atmosphere and stirred. Upon coolingto −78° C. in an acetone/CO₂ bath, dry pyridine (1.28 mL, 15.8 mmol) wasadded, resulting in the formation of a yellow precipitate. To thiscooled suspension was added a solution of 3,4-difluoropyrrole (1.49 g,14.4 mmol) in dichloromethane (3 mL) via syringe. The reaction wasallowed to stir for 3 h at −60° C., and then warmed to 0° C. over a 4 hperiod. The solution was then diluted with dichloromethane (20 mL) andwashed with hydrochloric acid (3 M, 2×50 mL). The biphasic system wasseparated off and the organic phase was collected and washed with water(50 mL) and brine (50 mL). The organic phase was then dried overanhydrous sodium sulfate, filtered and evaporated to dryness. The acidicaqueous phase from the initial extraction was extracted with ethylacetate (50 mL). The organic phase was separated off and washed withbrine (100 ml), dried over anhydrous sodium sulfate, filtered andevaporated to dryness. This afforded a green precipitate which waspurified by silica gel column chromatography (dichloromethane/ethylacetate, 95:5 to 90:10 (v/v) as eluent) to afford1,2-di(3′,4′-difluoropyrrol-2′-yl)ethanedione (405 mg, 21%) as a yellowpowder: m.p. 260-263° C. decomposed; ¹H NMR (500 MHz, DMSO d₆)δ7.43-7.46 (2H, m), 12.36 (2H, br s, NH); ¹³C NMR (125 MHz, DMSO d₆, ¹⁹Fdecoupled) δ110.7 (m), 113.3 (d, J 192 Hz), 136.8 (dd, J 9.1, 1.5 Hz),141.0 (t, J 8.2 Hz), 178.8; ¹⁹F NMR (470 MHz, DMSO d₆) δ−164.1, −177.9;HRMS (CI+) m/z (M+1) calcd for C₁₀H₅N₂O₂F₄: 261.0287, found: 261.0288.

EXAMPLE 24 2,3-Di(3′,4′-difluoropyrrol-2′-yl)quinoxaline

[0114] 1,2-Di(3′,4′-difluoropyrrol-2′-yl)ethanedione (112 mg, 0.43 mmol)and ortho-phenylenediamine (125 mg, 1.15 mmol) were dissolved in glacialacetic acid (20 mL). The resultant mixture was then heated at refluxunder an atmosphere of argon in the dark overnight. The reaction mixturewas evaporated to dryness under vacuum and the residue obtained waspurified using silica gel column chromatography (dichloromethane eluent)to afford 2,3-di(3′,4′-difluoropyrrol-2′-yl)quinoxaline (133 mg, 93%) asa yellow-green powder: m.p. 188-192° C.; ¹H NMR (500 MHz, DMSO d₆)δ6.94-6.98 (2H, m, pyrrole H), 7.80-7.84 (2H, m, quinoxaline H),8.01-8.05 (2H, m, quinoxaline H), 11.47 (2H, broad s, NH); ¹³C NMR (125MHz, DMSO d₆, ¹⁹F decoupled) δ104.0 (d, J 22 Hz), 111.1 (d, J 16 Hz),128.3, 130.3, 136.3 (dd, J 244, 11 Hz), 137.6 (dd, J 235, 11 Hz), 139.7,142.4; ¹⁹F NMR (470 MHz, DMSO d₆) δ−172.6 (dt, J 12.2, 3.3 Hz), -180.5(dt, J 12.6, 3.3 Hz); HRMS (CI+) m/z (M+1) calcd for C₁₆H₉N₄F₄:333.0763, found: 333.0754; Anal. Calcd for C₁₆H₈N₄F₄: C, 57.84; H, 2.43;N, 16.86. Found C, 57.71; H, 2.50; N, 16.81.

EXAMPLE 25 2,3-Di(3′,4′-difluoropyrrol-2′-yl)-6-nitroquinoxaline

[0115] 1,2-Di(3′,4′-difluoropyrrol-2′-yl)ethanedione (98 mg, 0.38 mmol)and 4-nitro-1,2-diaminobenzene (115 mg, 0.75 mmol) were dissolved inglacial acetic acid (30 mL) and the resultant solution was heated atreflux in the dark overnight under an atmosphere of argon. The solutionwas allowed to cool and evaporated to dryness in vaccuo. The residue waschromatographed over silica (chloroform) and the front running band wascollected to afford2,3-di(3′,4′-difluoropyrrol-2′-yl)-6-nitroquinoxaline (120 mg, 84%) as ared powder: m.p. 217-219° C. with decomposition; HRMS (CI+) m/z (M+1)Calcd for C₁₆H₇N₅F₄O₂ 378.06141, found 378.06206.

EXAMPLE 26 Preparation of1,2-di(5′-ethoxycarbonyl-3′,4′-dimethylpyrrol-2′-yl)ethanedione

[0116] A solution of 5′-ethoxycarbonyl-3′,4′-dimethylpyrrole (500 mg,2.99 mmol) in dry dichloromethane (10 mL) was cooled in an ice bathunder an atmosphere of argon. To this solution was added oxalyl chloride(220 mg, 1.79 mmol) and the solution was allowed to cool prior to theaddition of tin(IV) chloride (857 mg, 380 μL, 3.29 mmol). The resultantmixture was stirred at 0° C. for 1 h and then allowed to warm to roomtemperature over 1 h. The solution was then washed with water (2×50 mL),brine (50 mL), dried over anhydrous sodium sulfate, filtered andevaporated to dryness. The crude residue was then recrystallised from amixture of ethyl acetate/hexane, 1:9 v/v to afford1,2-di(5′-ethoxycarbonyl-3′,4′-dimethylpyrrol-2′-yl)ethanedione as alight green powder (128 mg, 22%): m.p. 210-212° C.; ¹H NMR (500 MHz,CDCl₃) δ1.39 (6H, t, J 7.1 Hz), 2.27 (6H, s), 2.34 (6H, s), 4.38 (4H, q,J 7.1 Hz), 10.93 (2H, br s, NH); ¹³C NMR (125 MHz, CDCl₃) δ9.7, 11.2,14.4, 61.0, 125.1, 126.9, 127.6, 133.4, 160.7, 179.5; HRMS (CI+) m/z(M+1) calcd for C₂₀H₂₅N₂O₆: 389.17126, found: 389.17092.

EXAMPLE 27 Preparation of1,2-di(4′-acetyl-3′,5′-dimethylpyrrol-2′-yl)ethanedione

[0117] A solution of 2,4-dimethyl-3-acetylpyrrole (1.48 g, 10.8 mmol) indry ether (180 mL) was cooled in an ice bath under an atmosphere ofargon. To this solution was added oxalyl chloride (720 μL, 8.1 mmol) andthe solution was then stirred at 0° C. for 1 h, then allowed to warm toroom temperature. The resultant dark-red-purple precipitate was thencollected on a frit and the filtrate was removed and the precipitate wasthen washed with dichloromethane (30 mL). Mass spectral analysisrevealed that the initial filtrate contained very little of the desiredcompound, however peaks at m/z (M+1) 210 and 228 can be attributed tomono-condensation with oxalyl chloride, followed by hydrolysis of theacid chloride to the acid, and mono-condensation product with oxalylchloride respectively. The dichloromethane washings of the precipitatecontained essentially only the desired product. The precipitate itselfalso contained essentially only the desired1,2-di(4′-acetyl-3′,5′-dimethylpyrrol-2′-yl)ethanedione (420 mg, 24%) asa purple solid. ¹H NMR (250 MHz, DMSO d₆) δ2.28 (3H, s), 2.40 (3H, s),2.53 (3H, s), 11.74 (2H, br s, NH); ¹³C NMR (125 MHz, DMSO d₆) δ12.3,14.5, 31.3, 123.5, 124.9, 132.0, 143.1, 183.4, 194.6; HRMS (CI+) m/z(M+1) calcd for C₁₈H₂₁N₂O₄: 329.15013, found: 329.15075.

EXAMPLE 282,3-Di(3′,5′-dimethyl-4′acetylpyrrol-2′-yl)-6-nitroquinoxaline

[0118] 1,2-Di(4′-acetyl-3′,5′-dimethylpyrrol-2′-yl)ethanedione (100 mg,0.30 mmol) and 4-nitro-1,2-diaminobenzene (79 mg, 0.52 mmol) weredissolved in glacial acetic acid (15 mL) and the resultant solution washeated at reflux in the dark overnight under an atmosphere of argon. Thesolution was allowed to cool and the evaporated to dryness in vaccuo.The residue was then taken up in chloroform (70 mL) and washed withhydrochloric acid (3 M, 3×40 mL), water (50 mL), sodium bicarbonatesolution (60 mL), brine (70 mL). The organic phase was then dried overanhydrous sodium sulfate, filtered and evaporated to dryness to afford34 mg of crude material.

EXAMPLE 29 Preparation of1,2-di(4′-heptanoyl-3′,5′-dimethylpyrrol-2′-yl)ethanedione

[0119] A solution of 2,4-dimethyl-3-heptanoylpyrrole (500 mg, 2.41 mmol)in dry dichloromethane (10 mL) was cooled in an ice bath under anatmosphere of argon. To this solution was added oxalyl chloride (183 mg,1.44 mmol, 125 μL) and the solution was then stirred at 0° C. for 1 h,then at r.t. for 2 h. The reaction mixture was diluted withdichloromethane (50 mL), and then washed with water (2×30 mL), brine (30mL), dried over anhydrous sodium sulfate, filtered, and evaporated todryness. Mass spec analysis of the crude product indicated the presenceof the desired compound,1,2-di(4′-heptanoyl-3′,5′-dimethylpyrrol-2′-yl)ethanedione. No furtherpurification was attempted. (CI+) m/z (M+1) C₂₈H₄₁N₂O₄ requires 469; 208(70), 252 (40), 280 (100), 298 (45), 469 (45). (CI−) m/z C₂₈H₄₀N₂O₄requires 468; 278 (28), 468 (100).

EXAMPLE 30 Preparation of 2,3-dipyrrol-2′yl-5,6-dicyanopyrazine

[0120] Diaminomaleonitrile (348 mg, 3.22 mmol) and 1,2-dipyrrol-2′-ylethanedione (500 g, 2.66 mmol) were dissolved in acetic acid (70 mL) andheated at reflux under an atmosphere of argon for overnight in the dark.The solvent was removed under vacuum and the residue was taken up in amixture of water (50 mL) and dichloromethane (100 mL). The organic phasewas separated off and the aqueous phase was extracted with furtherdichloromethane (2×40 mL). The organic phases were combined and washedwith saturated aqueous sodium bicarbonate solution (50 mL), water (50mL), then brine (50 mL). After drying over anhydrous sodium sulfate, theorganic phase was filtered and evaporated to dryness. Final purificationwas then effected using silica gel column chromatography(dichloromethane) to afford 2,3-dipyrrol-2′yl-5,6-dicyanopyrazine (65mg. 10%). ¹H NMR (250 MHz, DMSO d₆) δ6.17 6-6.25 (2H, m), 6.82-6.88 *2H,m), 7.12-7.18 (2H, m), 11.96 (2H, br s, NH; ¹³C NMR (62.5 MHz, CDCl₃)δ110.2, 114.5, 114.7m, 125.4, 126.3, 144.0; HRMS (CI+) m/z (M+1) calcd.For C₁₄H₉N₆: 261.08887, found: 261.08869.

EXAMPLE 31 Structure Determination of Fluoride Complexes X-ray StructureAnalysis

[0121] The molecular structure of compound 1 as well as itscorresponding tetrabutylammonium fluoride complex ([1•F]−) were deducedfrom single crystal X-ray diffraction analyses. The requisite singlecrystals were obtained from the slow evaporation ofdichloromethane/methanol (90/10: v/v) and neat dichloromethane solutionsof 1 and [1F]⁻•(Bu)₄N⁺ respectively. In both cases, the quinoxalinemoiety was found to possess the expected planar structure. As shown inFIG. 1 and FIG. 2, the two pyrrole subunits were found to be rotated insuch a way that they point out, in opposite directions, towards theexterior of the system.

[0122] While the structures of the fluoride complex and anion-freereceptor are quite similar, a major difference involves the hydrogenbonding network. The fluoride complex [1•F]⁻ presents a network thatinvolves 1) two pyrrolic NH subunits derived from two distinctdipyrrylquinoxaline units, 2) a fluoride anion and 3) a molecule ofwater. The net result is a planar network, wherein two identical planesare separated by a layer of tetrabulammonium cations, as shown inFIG. 1. By contrast, the structure of the fluoride-free system reveals ahydrogen bonding network that serves to arrange the dipyrrylquinoxalinemoieties into layers wherein a molecule of water bridges two pyrrolic NHgroups from two distinct molecules. In this instance, it is also worthnoting that, in addition to the conventional N . . . O hydrogen bondinginteractions, one hydrogen atom of the bridging water molecule isdirected at the centroid of a pyrrole ring. The result of thisinteraction is that the molecules from two different planes are relatedby a two-fold screw axis.

[0123] In the case of the fluoride complex [1•F]⁻, the tightness of thehydrogen bonds is highlighted by the short F . . . N distance: Thesedistances are 2.629(2) and 2.640(2) Å respectively, and are, in fact,shorter than the corresponding F N distances (2.790(2) Å) observed inthe case of calixpyrrole fluoride anion complex (Dietrich, et al.,1981).

EXAMPLE 32 Spectroscopic Studies-Colormetric Assay for Anion Binding

[0124] The conclusion that 1 binds fluoride anion in dichloromethanesolution was further supported by mass spectrometric analyses andtitration experiments made using UV-visible absorption and fluorescenceemission methods (Tables 1 and 2). The latter studies, which providedK_(a) values (Tables 1 and 2), were complemented by molar ratio analyses(Job plots) with 1:1 binding stoichiometries observed in all cases.

[0125] In order to analyze compounds having only one pyrrolic nitrogen,a mono SEM protected analogue (12) was prepared as described in Example6. Additionally, quinoxaline (11) was used in the analysis.

[0126] The results are as shown in the following tables: TABLE 1Spectroscopic properties of 2,3-dipyrrylquinoxaline 1, dipyrrylethanedione 10, 6,7-dimethoxy-2,3-dipyrrylquinoxaline 2,6,7-dinitro-2,3- dipyrrylquinoxaline 3, 6-nitro-2,3-dipyrrylquinoxaline7, and quinoxaline 11. All values measured in dichloromethane. MonoSE2,3-di- Dipyrryl M-2,3-di- pyrryl ethane- Di- Mono- pyrrylquin- Quin-quinoxaline dione methoxy nitro Dinitro oxaline oxaline 1 10 2 7 3 12 11λ_(max)(ex) 412 nm 341 nm 414 nm 450 nm 460 nm 396 nm 315 nmλ_(max)(em)^(a) 490 nm 458 nm 475 nm 600 nm 620 nm 492 nm 403 nm ε17,110 16,200 15,900 18,730 29,200 14860 6,222 (at λ_(max)) M⁻¹cm⁻¹M⁻¹cm⁻¹ M⁻¹cm⁻¹ M⁻¹cm⁻¹ M⁻¹cm⁻¹ M⁻¹cm⁻¹ M⁻¹cm⁻¹

[0127] TABLE 2 Anion binding constants (K_(a)) for2,3-dipyrrylquinoxalines 2, 3 and 7 and control compounds 1, 10 and11^(a) 2,3- Mono SEM- dipyrrylquin- Dipyrryl 2,3-dipyrryl oxalineethanedione Dimethoxy Mononitro Dinitro quinoxaline Anion 1^(b) 10^(c) 27 3 12 F 18,200 M⁻¹ 23,000 M⁻¹ 2,300 M⁻¹ 118,000 M⁻¹ 117,000 M⁻¹ 2,300M⁻¹ H₂PO₄ ⁻ 60 M⁻¹ 170 M⁻¹ <50 M⁻¹ 80 M⁻¹ 55 M⁻¹ <50 M⁻¹ Cl⁻ 50 M⁻¹ <50M⁻¹ <50 M⁻¹ 45 M⁻¹ 45 M⁻¹ <50 M⁻¹

[0128] In terms of specifics, we found that in dichloromethane solution,the diketone precursor, 10, displays a relatively large extinctioncoefficient whereas its fluorescence emission is minimal. Under the sameconditions, quinoxaline itself, 11, displays a relatively low extinctioncoefficient. Nonetheless, even with these control systems the additionof tetrabutylammonium salts of various anions (F⁻, Cl⁻ and H₂PO₄ _(⁻) ),gave rise to results that were quite interesting. In the case of 11 (indichloromethane), the addition of F⁻, Cl⁻ and H₂PO₄ _(⁻) did not induceany significant change in the absorbance or emission spectra. Bycontrast, in the case of 10 remarkable changes were noticed in theemission spectra when either F⁻ or H₂PO₄ _(⁻) were added. As a matter offact, in the presence of F⁻, a significant decrease and a shift in theabsorbance intensity could be observed visually with the color of thesolution changing from yellow-green to orange. Such effects can berationalized in terms of the electron withdrawing nature of the twocarbonyl groups, which serve to pull the electrons from the pyrroleunits and thus act to increase the acidity of the pyrrolic NH protons.As a result, hydrogen bonding interactions with F⁻ are favored. In theparticular case of inorganic phosphate, we speculate that the twocarbonyl groups may also be involved in binding, stabilizing the complexvia ancillary hydrogen bonding interactions involving the twoHOP-phosphate protons.

[0129] Unfortunately, the fluorescence quantum yield of 10 is low. Thuswe considered that 2,3-dipyrrylquinoxaline system 1 derived from it aswell as its analogues 2, 3, and 7 might prove to be far better sensors.Not only should they display high affinities toward fluoride anion indichloromethane solution, but they were expected to exhibit even moredramatic fluoride anion induced color changes as measured by absorptionand emission spectroscopy, as well as naked eye color detection. Assummarized in Table 2, this expectation is indeed realized in the caseof 1, 3, and 7, with the latter two systems showing very dramatic yellowto purple fluoride anion-induced colorimetric responses.

[0130] The greater “success” of 3 and 7 relative to 1 and 2, a systemthat hardly “works” at all in terms of colorimetric F⁻ signaling, is notreally surprising considering that the relative electron deficiency ofthe mono- and dinitro derivatives should lead to increase in theirhydrogen bonding donating character. Indeed, both 3 and 7 displayaffinity constants (K_(a)), for F⁻ binding in dichloromethane (ca 10⁵M⁻¹), that are quite high. By contrast, 1 (K_(a)=2×10⁴ M⁻¹) and 2(K_(a)=2×10³ M⁻¹) display affinity constant that are much lower.Interestingly, even in the case of the high affinity systems 3 and 7 anexcellent selectivity for fluoride anion is maintained; indeed, theselectivity ratio for F⁻ over Cl⁻ is more than 360.

[0131] In addition to the specific pyrrole-quinoxalines, the usefulnessof the general pyrrole-aryl structures as sensing compounds has beendemonstrated. Using 2,3-dipyrrol-2′yl-5,6dicyanopyrazine (preparation isdescribed in Example 30) as a sensing compound, a vivid yellow-to-redcolor change in solution observed upon addition of fluoride ion verifiesthat the quinoxaline backbone is not essential for chemical sensing inthis family of compounds. This is consistent with the theory thatchanges in orbital overlap between the pi systems of conjugated bridgingunit and the pyrrole rings account for the sensitivity of the sensingelements to analyte species.

EXAMPLE 33 Mechanistic Studies of Fluoride Anion Binding

[0132] In order to understand more fully the above results, studies wereperformed to map out the mode of fluoride anion binding. Firstly, it wasverified that two pyrrolic nitrogens are required to observe theanion-induced color change. Toward this end, the mono protected2,3-dipyrrylquinoxaline 12 was prepared by reacting 0.8 equivalents ofSEMCl with one equivalent of 2,3-dipyrrylquinoxaline. (See Scheme 2illustrating mono SEM protection of 2,3-dipyrrylquinoxaline.) Indichloromethane, this mono-protected adduct showed no color change whentreated with tetrabutyl ammonium fluoride.

[0133] The next series of mechanistic studies involved carrying outtemperature dependent NMR measurements (room temperature to −80° C.).These revealed little out of the ordinary (i.e., no temperaturedependent chemical shift changes were observed) and are consistent witha single atropisomer of 1 being present in solution. Further studiesinvolve X-ray diffraction analysis with the realties as shown in Table3. TABLE 3 Selected bond distances (Å) and bond angles from X-ray 1 [1 ·F] N—H . . . H—N 6.562 6.892 N . . . N 5.766 5.763 H_(α). . . H_(α)8.795 8.746 H_(β2). . . H_(β2) 2.607 2.612 F . . . H—N1 — 1.639 F . . .H—N2 — 8.196

EXAMPLE 34 Analogues of Pyrrole-Aryls for Metal Binding and AlteredFluorescence Properties

[0134] Analogues of the pyrrole-aryls may be prepared to form metalcomplexes as shown below. By reaction of 9 with a1,10-phenanthroline-5,6-dione, a compound represented by 13 may besynthesized. Compounds exemplified by 13 and 14 are contemplated for theability to complex a metal through the phenanthroline unit.

[0135] Similar analogues may be synthesized using the appropriate1,2-diamines to produce compounds such as 15 and 16 for alteredfluorescence/binding properties.

[0136] Additionally, using a porphyrin 1,2-diones, compounds exemplifiedby structure 17 can be generated as shown below:

[0137] wherein R₁-R₁₀ are as described previously and representativemetals include Li, B, Na, Mg, Al, Si, K—As, Rb—Sb, Cs—La, Hf—Bi, pr, Eu,Yb and Th.

EXAMPLE 35 Post-Synthetic Modification of the ‘Parent’2,3-Dipyrrol-2′-yl-quinoxaline

[0138] A wide variety of substituents may be introduced to the pyrrolequinoxaline post-synthetically at the α-pyrrolic positions as shown withthe following selected examples.

[0139] with any of R₁-R₂, R₃-R₄ may be as follows:

R₃═R₄═I, R₃═R₄═Br, R₃═R₄═COCH₃, R₃═R₄═CHO

[0140] As shown in Scheme 4 below.

[0141] One of skill in the art will further recognize that the diiodo orthe dibromo compounds may be modified through known synthetic means togenerate a range of α-substituted compounds as exemplified by structures19.

[0142] Methods are also available for the synthesis of a TMS derivativeas shown below:

[0143] Removal of the TMS group and subsequent reaction with a metalsalt, as described previously, will afford metal linked systems.

EXAMPLE 36 The Starting Pyrrole Unit as a Source of Variation

[0144] It will be apparent to one of skill in the art that manypyrrolylquinoxalines may be obtained within the context of the presentinvention. For example, as shown below, various substituents may beintroduced on the starting pyrrole to generate a series of diones. Thesediones are then used in the synthesis of pyrrole-aryls to effect desiredproperties, such as a particular anion specificity, or increasedsolubility in a specific solvent. Accordingly it is contemplated thatvariety of approaches may be employed, in accordance with the presentinvention, to prepare an array of diones with a wide variety ofsubstituents as represented in Scheme 5 below.

[0145] It is further envisioned that different combinations ofpolypyrroles, in particular bipyrroles and terpyrroles, may be employedin the reaction with oxalyl chloride to produce various dione analoguesas represented below.

EXAMPLE 37 Incorporation into Macrocycles

[0146] It is contemplated that the remaining α-free position on thepyrrole rings may react under a variety of conditions as shown below, toprovide a number of novel compounds with a pyrrole-aryl and amacrocyclic component. These macrocycles may be used in fields such asanion binding (26), cation binding (28, 31, 32) and in optical devices(26, 28, 31, 32) and molecular wires (28, 31, 32). In the followingexamples, R₁-R₄ are as previously described, n=0-10 with the preferredcompound(s) as indicated within the synthetic scheme.

[0147] R₄═H, n=1

[0148] It should again be stressed that although not shown above, all ofthe reaction schemes can be applied to analogues having widelysubstituted pyrrole rings. The pyrroles may be substituted both α and β,or in both ways to the pyrrole nitrogen atoms. The above reactionschemes are not intended to be limited to unsubstituted pyrroles or tothe substitutions shown.

EXAMPLE 38 Alternate Heterocycles in the Starting Diketone

[0149] It is contemplated that alternate heterocyclic diones may be usedin a condensation reaction with aryl 1,2-diamines, as outlined inprevious examples, to produce 2,3-heteroaryl quinoxaline analogues. Itis believed that these compounds will act as effective sensors for avariety of cations or neutrals. Compounds 33-38 below represent someproposed alternative diones contemplated for use in accordance with thepresent invention.

EXAMPLE 39 Dianions as Ligands

[0150] The pyrrole-aryls of the present invention may be used as sensorsfor anions, cations or neutral molecules provided the compound is of theappropriate charge of polarization. For instance, pyrrole-aryls of thepresent invention are contemplated for use as metal cation chelants byremoving protons from the pyrrolic nitrogens as shown below.

EXAMPLE 40 Pyrrole-Aryls As Anion Sensing Agents

[0151] The compounds of the present invention are used as anion sensorsin a variety of applications including, chromatography, anionquantification, ion-selective electrodes and fiber-optics. A preferredexample for use of the present compounds is for selective anion sensing,in particular fluoride sensing. Fluoride sensing has largely beencomplicated by competition from other biologically common species suchas hydroxide, chloride and phosphate. The ability to sense fluoride isimportant for the analysis of drinking water, as well as ground water,in biological systems such as teeth and bones and in certain diseasestates such as fluorosis. In vitro sensing for fluoride is alsoimportant, for example to determine the amount of damaging fluorocarbonsin the atmosphere and even the presence of fluorinated phosphates whichcan be used as chemical weapons due to their toxicity when ingested. Thecompounds of the present invention provide a distinct advantage overother sensors due to the selectivity for fluoride ion as demonstrated inExamples 7-9 and the dramatic color change produced upon binding. Thismakes the compounds particularly amenable for use in paper based sensingsuch as litmus paper, solid support sensing and as a coating on eitherfiber optic wires or electrodes. Selective sensing and separation arealso contemplated using chromatographic methods. For example the presentcompounds may be coupled to a solid- support and used to separatevarious anions from each other and from other species in the mixture. Incertain circumstances a desired anion may even be collected as thesystem is entirely reversible based on the environment. Washing underappropriate conditions completely removes fluoride anion and returns themolecule to its original state.

[0152] It will also be apparent to one of skill in the art that manyderivatives and analogues may be obtained within the context of thedisclosed methods and compounds.

[0153] Once a range of pyrrole-aryl or alternate heterocyclic analogueshave been generated, as described herein in the foregoing detailedexamples, the specificity, kinetics and thermodynamics of anion bindingunder a range of conditions and with an array of different anions may bedetermined. The structure and function of the most promising compoundsmay then be optimized so that they bind the desired anion under theappropriate conditions, solvent, temperature, affinity pH etc., tofunction as an efficient sensor.

EXAMPLE 41 Synthesis of Water Soluble Pyrrole-Aryl Analogues

[0154] It is contemplated that the addition of charged groups and/orpolar groups such as glycols or polyglycols to the2,3-dipyrrylquinoxaline core will impart solubility in aqueoussolutions. The synthesis of such a compound is outlined in the schemebelow. The compound is that of 5 from Example 1.

[0155] It is further contemplated that the addition of further pyrrolesto the quinoxaline subunit will result in the increase of solubility inaqueous solutions. The synthesis of such compounds is illustrated in thefollowing schemes.

[0156] It is expected that these compounds will serve as sensors andtherapeutic agents in aqueous solutions as described in the nextexample.

EXAMPLE 42 Anion Binding Compounds as Therapeutic Agents

[0157] The compounds of the present invention, in particular thosecompounds with increased solubility in aqueous solutions arecontemplated to be of use as in vivo anion sensors, for example bloodsamples, and as therapeutic agents to bind excess anion in certaindisease states such as fluorosis.

[0158] To develop pyrrole-aryl compounds of the present invention foruse as therapeutic agents, in vitro tests will be first conducted todetermine the efficiency of binding, retention and selectivity inaqueous solutions. These will follow similar protocols as previouslydescribed for screening in organic solvents.

[0159] Following such in vitro tests, the binding activity of promisingcompounds will be followed up, in for example biological fluids such asblood, and then in in vivo animal studies. These studies will beconducted according to the standard practice for such animal trials, theexecution of which will be ell known to one of skill in the art.

[0160] During the animal trials, the compounds may be further modifiedif required. They may be modified to increase solubility or to overcomein vivo degradation. Alternatively, if such problems occur, thecompounds may be enveloped within a bio-compatible liposome and thenadministered intravenously.

[0161] Toxicity studies will also be carried out at this stage. Themethods for determining both acute and chronic toxicity will be wellknown to one of skill in the art. Toxicity can be investigated inrelation to solubility, net charge at physiological pH and changes insubstituents.

[0162] All of the compositions and methods disclosed and claimed hereincan be made and executed without undue experimentation in light of thepresent disclosure. While the compositions and methods of this inventionhave been described in terms of preferred embodiments, it will beapparent to those of skill in the art that variations may be applied tothe compositions and methods and in the steps or in the sequence ofsteps of the method described herein without departing from the concept,spirit and scope of the invention. More specifically, it will beapparent that certain agents which are both chemically andphysiologically related may be substituted for the agents describedherein while the same or similar results would be achieved. All suchsimilar substitutes and modifications apparent to those skilled in theart are deemed to be within the spirit, scope and concept of theinvention as defined by the appended claims.

EXAMPLE 43 Sensing Compound Immobilized on a Solid Support

[0163] The usefulness of the pyrrole-aryl compounds as sensing agentswhen bound to solid supports was demonstrated by visual color change inthe presence of tetrabutylammonium fluoride.2,3-Dipyrrol-2′-yl-6-carboxyquinoxaline (preparation is described inExample 19) was immobilized on a polystyrene beads functionalized withpolyethylene glycol groups that terminate in an amine. The quinoxalineis linked to TG-amino resin through an amide bond through a condensationreaction. An acetyl derivatized bead was used a blank.

[0164] The presence of fluoride ion was signaled by a dramatic visualcolor change from yellow to red for the2,3-dipyrrol-2′-yl-6-carboxyquinoxaline-fuctionalized bead. The blankbead was initially colorless and remained so upon addition of fluorideion.

REFERENCES

[0165] The following references, to the extent that they provideexemplary procedural or other details supplementary to those set forthherein, are specifically incorporated herein by reference.

[0166] Gale et al. Chem. Commun. 1998, 1-8.

[0167] Dietrich, B.; Hosseini, M. W. in Supramolecular Chemistry ofAnions; Bianchi, A., Bowman-James, K. and García-Españia, E., Ed.;Wiley-VCH: New York, 1997, pp 45-62.

[0168] Schmidtchen, F. P. Nachr. Chem, Tech. Lab. 1988, 36, 8-17.

[0169] K. L. Kirk Biochemistry of the Halogens and Inorganic HalidesPlenum Press: New York, 1991, p 58.

[0170] B. L. Riggs Bone and Mineral Research, Annual 2 Elsevier:Amsterdam, 1984, pp 366-393.

[0171] M. Kleerekoper Endocrinol. Metab. Clin. North Am. 1998, 27,441-452.

[0172] A. Wiseman Handbook of Experimental Pharmacology XX/2.; Part. 2,Springer-Verlag: Berlin, 1970, pp 48-97.

[0173] Sessler, J. L.; Andrievsky, A.; Genge, J. W. in Advances inSupramolecular Chemistry; Lehn, J. M., Ed.; JAI Press Inc., 1997; Vol.4, pp 97-142.

[0174] Gale, P. A.; Sessler, J. L.; Král, V. K.; Lynch, V. M. J. Am.Chem. Soc. 1996, 118,5140-5141.

[0175] Sessler, J. L.; Gale, P. A.; Genge, J. W. Chem. Eur. J. 1998, 4,1095-1099.

[0176] Dietrich, B.; Hosseini, M. W.; Lehn, J. M.; Sessions, R. B. J.Am. Chem. Soc. 1981, 103, 1282-1283.

[0177] Hosseini, M. W.; Lehn, J. M. Helvetica Chimica Acta 1988, 71,749-756.

[0178] Dietrich, B.; Fyles, D. L.; Fyles, T. M.; Lehn, J.-M. HelveticaChimica Acta 1979, 62, 2763-2787.

[0179] Metzger, A.; Lynch, V. M.; Anslyn, E. V. Angew. Chem. Int. Ed.Engl. 1997, 36, 862-865.

[0180] Oddo, B. Gazz. Chim. Ital. 1911, 41, 248-255.

[0181] Behr, D.; Brandänge, S.; Lindström, B. Acta Chem. Scand. 1973,27, 2411-2414.

[0182] Sessler, J. L.; Mody, T. D.; Ramasamy, R.; Sherry, A. D. New J.Chem. 1992, 16, 541-544.

[0183] Cheeseman, G. W. H. 1962, J. Chem. Soc., 1170-1176.

What is claimed is:
 1. A pyrrole-aryl compound of the general formulas,

wherein Ar is an aryl group, wherein R₁-R₆, individually at eachoccurrence, are the same or different, and are hydrogen, alkyl,hydroxyalkyl, glycol, polyglycol, amino, nitro, halo, cyano, aryl,heteroaryl, thio, thioalkyl, amide, ester, acyl, aldehyde, or carboxy,and provided, however, that if Ar is an unsubstituted quinoxaline groupthen R₁-R₆ cannot each be hydrogen.
 2. A pyrrole-aryl compound of thegeneral formula:

wherein R₁-R₁₀, individually at each occurrence, are the same ordifferent and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy, provided, however, that R₁-R₁₀ cannoteach be hydrogen.
 3. The compound of claim 2, wherein R₁═R₂═OCH₃.
 4. Thecompound of claim 2, wherein R₁═R₂═NO₂.
 5. The compound of claim 2,wherein R₁═R₂═CH₃.
 6. The compound of claim 2, whereinR₁═R₂═O(CH₂CH₂O)₃CH₃.
 7. The compound of claim 2, whereinR₁═R₂═O(CH₂)_(n)CH₃, and wherein n is 0-20.
 8. The compound of claim 2,wherein R₁═H, R₂═NO₂.
 9. The compound of claim 2, wherein R₁═NH₂,R₂═NO₂.
 10. The compound of claim 2, wherein R₁═NH₂, R₂═NH₂.
 11. Thecompound of claim 2 wherein R₁ and R₂ are part of a cyclic group andfurther wherein said compound is selected from the group consisting of:


12. The compound of any one of claims 1-11 in which one or more of thepyrrole nitrogens exist in anionic form.
 13. A compound of the generalformulas,

wherein individually at each occurrence, each of R₁, -R₆ are the same ordifferent, and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy.
 14. The compound of claim 13, whereinR₁═CO₂CH₂CH₃, R₂═CH₃, R₃═CH₃.
 15. The compound of claim 13, whereinR₁═CO₂CH₂CH₃, R₂═CH₂CH₃, R₃═CH₂CH₃.
 16. The compound of claim 13,wherein R₁═CH₃, R₂═COCH₃, R₃═CH₃.
 17. The compound of claim 13, whereinR₁═CH₃, R₂═CO(CH₂)_(n)CH₃, R₃═CH₃, and wherein n is 0-20.
 18. Thecompound of claim 13, wherein R₁═H, R₂═CH₃, R₃═CH₃.
 19. The compound ofclaim 13, wherein R₁═H, R₂═CH₂CH₃, R₃═CH₂CH₃.
 20. The compound of claim13, wherein R₁═H, R₂═R₃═CH₂(CH₂)₂CH₃.
 21. The compound of any one ofclaims 13-20 in which one or more of the pyrrole nitrogens exist inanionic form.
 22. A compound of the general formula,

wherein individually at each occurrence, each of R₁, -R₇ are the same ordifferent and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy, and n=0-10, and further wherein eachof R₁-R₇ on either side of the axis of the diketone bridge may be thesame or different from the corresponding R₁-R₇ on the opposite side ofthe diketone bridge and further wherein each R₄ and R₅ of the n subunitsof pyrrole may be the same or different from corresponding R₄ and R₅ ofany other subunits of pyrrole.
 23. The compound of claim 22, whereineach of R is H and wherein n=0.
 24. A compound of the general formula:

wherein individually at each occurrence, each of R₁, -R₁₁ are the sameor different and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy, and n=0-10, and further wherein eachof R₁-R₇ on either side of the axis of the quinoxaline bridge may be thesame or different from the corresponding R₁-R₇ on the opposite side ofthe quinoxaline bridge and further wherein each R₄ and R₅ of the nsubunits of pyrrole may be the same or different from corresponding R₄and R₅ of any other subunits of pyrrole.
 25. The compound of claim 24wherein n=1.
 26. The compound of claim 24 wherein n=2.
 27. Apyrrole-aryl compound of the general structure:

wherein individually at each occurrence, R₁, -R₁₀ are the same ordifferent and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy and M is Li, B, Na, Mg, Al, Si, K, As,Rb, Sb, Cs, La, Hf, Bi, Pr, Eu, Yb, or Th.
 28. A pyrrole-aryl compoundof the general structure:

wherein R₁, -R₈ individually at each occurrence, are the same ordifferent and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy; and further wherein Ar is selectedfrom the group consisting of:

 and further wherein X, Y, and Z are selected from the group consistingof hydrogen, aldehyde, nitro, and amino.
 29. A pyrrole-quinoxalinecompound of the general structure:

wherein R₁, -R₈ individually at each occurrence, are the same ordifferent and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy, and wherein TMS is a trimethylsilylgroup.
 30. The compound of claim 1, 2, 24, 27, or 28 in which one ormore of the pyrrole nitrogens exist in anionic form.
 31. The compound ofclaim 1, 2, 24, 27, or 28 incorporated into a macrocyclic molecule. 32.The compound of claim 31 selected from the group consisting of thefollowing structures:

wherein all R, individually at each occurrence, are the same ordifferent and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy and n=1-10.
 33. A pyrrole-arylcompound of the following general formulas:

wherein R₁-R₆, individually at each occurrence, are the same ordifferent and are hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol,amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide,ester, acyl, aldehyde, or carboxy.
 34. A method for the analysis of ananion or neutral species comprising: (a) obtaining a pyrrole-arylcompound; (b) contacting the pyrrole-aryl compound with a samplecontaining an anion or neutral species; and (c) optically monitoring thepyrrole-aryl compound in the presence of the sample.
 35. The method ofclaim 34 wherein said pyrrole-aryl compound is a pyrrole-quinoxalinecompound.
 36. The method of claim 34 or 35, wherein the pyrrole-arylcompound is the compound of claim
 2. 37. The method of claim 36, whereinR₁═R₂═NO₂.
 38. The method of claim 36, wherein R₁═H, R₂═NO₂.
 39. Themethod of claim 34 or 35 wherein the anion is an anion of fluoride,cyanide, phenolate, carboxylate, sulfate, sulfite, sulfide, sulfonate,nitrate, nitrite, bromide, iodide, pertechtenate, perrhenate, phosphate,phosphonates, nucleobase, nucleotide or oligonucleotide.
 40. The methodof claim 39, wherein the anion is fluoride or chloride.
 41. The methodof claim 34 or 35 wherein the neutral species is cis-3-hexenal.
 42. Themethod of claim 34 or 35, wherein the optically monitoring isfluorescence excitation, fluorescence emission, visual detection orultraviolet or visible absorption.
 43. The method of claim 34 or 35,wherein the pyrrole-aryl compound is attached to a solid support. 44.The method of claim 34 or 35, wherein the optical monitoring isperformed by the means of a spectroscopic apparatus comprising a fiberoptic.
 45. The method of claim 34 or 35, in which the analysis iscarried out in vivo, in vitro, or in situ.
 46. A method of using apyrrole-aryl compound in vivo, in vitro, or in situ to selectivlelytransport therapeutic agents.
 47. A method of using a pyrrole-arylcompound as a sensing element in the analysis of foodstuffs.